JP2014236606A - System interconnection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system interconnection system capable of changing the target value of bus voltage quickly.SOLUTION: Upon reaching a time tx, an AC voltage value goes above a reference waveform Vth(n), and since the percentage modulation MR(n) goes above 0.97, a bus voltage correction determination routine sets the increase command information of a target voltage value Vdc. Consequently, at the next zero-cross timing t4, a new reference percentage modulation MR(n+1) and a target voltage value Vdc(n+1) are set, and a signal generation unit 152a generates a drive signal by using them.

Description

  The present invention relates to a grid interconnection device, and more particularly to bus voltage control of a DC link unit.

  The grid interconnection device is installed so as to be interposed between the distributed power supply and the grid power supply. The grid interconnection device converts power generated by a distributed power source from DC to AC, and supplies the AC power to a system power source and a load connected to the system power source.

  In the grid interconnection device, the output current of the inverter circuit is controlled while monitoring the AC power supply voltage (or a value corresponding thereto) in order to supply the generated current to the system power supply. This output current is covered by the electric charge accumulated in the smoothing capacitor of the converter circuit, and is greatly influenced by the voltage value (bus voltage value) of the smoothing capacitor.

In response to this, in Japanese Patent Laid-Open No. 11-122818 (Patent Document 1), the boosted voltage of the converter circuit is controlled based on the system voltage (AC power supply voltage). In this technique, as shown in FIG. 7, a threshold Vth (n) for the system voltage Vac is provided, and a target voltage Vdc (n) somewhat higher than this threshold is set.
In the figure, Vdc (n) = Vth (n) + ΔVj.
Vdc (n): set target voltage Vth (n): set threshold value ΔVj: offset value (a value considering ripple fluctuation)

According to the technique of Patent Document 1, when the grid voltage Vac exceeds the threshold value Vth (see times t3 to t4), the grid interconnection device grasps the rising fluctuation of the grid voltage Vth and issues a command to increase the target voltage Vdc. put out.
In the figure, Vdc (n + 1) = Vdc (n) + ΔVh.
Vdc (n + 1): target voltage after setting change ΔVh: correction value of target voltage

  As shown in the figure, the set value of the target voltage Vdc (n + 1) after the change is changed as needed in response to the fluctuation of the system voltage Vac, and an offset amount ΔVj between the boosted voltage of the converter circuit and the system voltage Vac is secured. According to the description in Patent Document 1, by maintaining such a relationship, the boosted voltage is always controlled to be higher than the system voltage Vac, and it is possible to avoid superimposing harmonics on the current waveform of the output current. It is explained.

JP-A-11-122818

  However, as shown in FIG. 7, if the threshold value Vth is set by the offset amount with respect to the target voltage Vdc, the monitoring function of the system voltage Vac determines the fluctuation state for the vicinity of the peak value Vp of the system voltage Vac due to its nature. I have to. That is, in such a technique, unless the peak value Vp (or the vicinity thereof) is reached, there is a problem that it cannot be determined whether or not the system voltage Vac being monitored is fluctuating greatly.

  For example, as shown in FIG. 8A, when the system voltage Vac fluctuates at time tx, the grid interconnection device detects this fluctuation after the peak value Vp (or its vicinity). Unless the next peak value Vp (time t4 to t5) is reached, fluctuations in the system voltage Vac cannot be detected. For this reason, the target voltage Vdc is not changed before the peak value at time t4 to t5, and the control with the changed target voltage Vdc is performed after the time t5 to t6. In such a case, the target voltage is not changed before the peak value at times t4 to t5, so that the bus voltage and the system voltage Vac are allowed to approach, and a harmonic is formed in the output current Iac of the inverter circuit. (See FIG. 8b, times t4 to t5).

  Further, as shown in FIG. 9A, when the system voltage Vac fluctuates before the peak value Vp (see time ty), the target voltage Vdc cannot be changed unless the peak value Vp in the waveform is reached. In the vicinity of the peak value Vp, the bus voltage and the system voltage Vac are allowed to approach each other. For this reason, there is a danger that the output current Iac is caused to generate a harmonic corresponding to the peak time of the system voltage Vac at times t3 to t4 (see FIG. 9b).

  Thus, when the threshold value Vth is set by the offset amount with respect to the target voltage Vdc, the timing for changing the target voltage Vdc is delayed. For this reason, there arises a problem that harmonics are superimposed on the output current Iac of the inverter circuit before the target voltage Vdc is switched from the sudden change times tx and ty of the system voltage Vac. Such harmonics are considered to be a factor causing deterioration in the quality of the system power supply, and various guidelines are instructed to remove them.

  In addition, in the DC link section connecting the converter circuit and the inverter circuit, the voltage value Vdc (ins) at the DC link section is accompanied by a large period fluctuation according to the deterioration of the smoothing capacitor (electrolytic capacitor). . In this case, in the grid interconnection device according to the conventional example, a situation is formed in which the voltage value Vdc (ins) at the DC link portion is temporarily lower than the voltage value Vac of the grid power supply. As a result, the quality of the output current caused by the reverse flow of the current will be reduced.

  In view of the above problems, an object of the present invention is to provide a grid interconnection device that can quickly change a target value of a bus voltage.

In order to solve the above-mentioned problem, the first invention has the following system interconnection device configuration. That is, a converter circuit that boosts supply power supplied from a distributed power source, an inverter circuit that converts DC power output from the converter circuit into AC power, and reversely flows the AC power to a system power source, and the converter circuit The DC signal is relayed from the inverter circuit to the inverter circuit and the bus voltage changes according to the operation of both circuits, and the drive signal input to each of the converter circuit and the active element group provided in the inverter circuit is A control circuit to be generated,
The control circuit includes an AC voltage value acquisition unit that generates AC voltage value data corresponding to the voltage value of the system power supply, and an AC voltage value parameter setting unit that sets an AC voltage value parameter corresponding to the AC voltage value data. A reference voltage value parameter setting unit for setting a reference voltage value parameter corresponding to a voltage value of a substantially similar reference waveform with respect to the AC voltage waveform of the system power supply, and the magnitude of the AC voltage value parameter and the reference voltage value parameter A function of a target bus voltage correction unit that corrects the target value of the bus voltage based on the relationship and a signal generation unit that generates the drive signal using the corrected target value are constructed.

Preferably, in the first invention, the AC voltage value parameter is AC modulation rate value information calculated from the AC voltage value data and DC detection value data of the bus voltage,
The reference voltage value parameter is reference modulation factor value information calculated from reference voltage value data representing the voltage value of the reference waveform and DC detection value data of the bus voltage.

  Preferably, in the first invention, the target bus voltage correction unit compares the AC modulation factor value information and the reference modulation factor value information to determine a correction command type, and the correction command. And a bus voltage correction amount setting program for determining a correction amount to be applied to the target value of the bus voltage based on the above.

  Preferably, in the first invention, the reference modulation factor value information is constituted by a plurality of reference modulation factor value information provided corresponding to different modulation factors.

  Preferably, in the first invention, the plurality of reference modulation factor value information includes first reference modulation factor value information used when setting increase command information as to whether or not to increase the correction amount, and the correction. It is assumed that second reference modulation factor value information used when setting reduction command information for determining whether or not to reduce the amount is provided.

  Preferably, in the first invention, the bus voltage correction determination program uses a second correction waiting time required to decrease the correction amount, rather than a first correction waiting time required to increase the correction amount. It is assumed that it is set long.

Moreover, in 2nd invention, it is set as the structure of the following grid connection apparatuses. That is, a converter circuit that boosts supply power supplied from a distributed power source, an inverter circuit that converts DC power output from the converter circuit into AC power, and reversely flows the AC power to a system power source, and the converter circuit The DC signal is relayed from the inverter circuit to the inverter circuit and the bus voltage changes according to the operation of both circuits, and the drive signal input to each of the converter circuit and the active element group provided in the inverter circuit is A control circuit to be generated,
The control circuit includes an AC voltage value acquisition unit that generates AC voltage value data corresponding to the voltage value of the system power supply, and reference voltage value data that represents a voltage value of a reference waveform that is substantially similar to the AC voltage waveform of the system power supply. A reference voltage value data setting unit in which is set, a target bus voltage correction unit that corrects the target value of the bus voltage based on the magnitude relationship between the AC voltage value data and the reference voltage value data, and the corrected target value A signal generation unit that generates the drive signal using the function is constructed.

  Preferably, in the second invention, the target bus voltage correction unit compares the AC voltage value data and the reference voltage value data to determine a correction command type, and based on the correction command Then, a bus voltage correction amount setting program for determining a correction amount to be given to the target value of the bus voltage is started.

  Preferably, in the second invention, the reference voltage value data is constituted by a plurality of reference voltage value data provided corresponding to different ratios.

  In a second aspect of the present invention, preferably, the plurality of reference voltage value data includes the first reference voltage value data used when setting increase command information as to whether or not to increase the correction amount, and the correction amount. It is assumed that second reference voltage value data used when setting reduction command information as to whether or not to decrease is provided.

  Preferably, in the second invention, the bus voltage correction determination program is configured such that the second correction waiting time required to decrease the correction amount is greater than the first correction waiting time required to increase the correction amount. It is assumed that it is set long.

  According to the grid interconnection device according to the present invention, since the reference value is set using waveform data similar to the grid voltage, when an event that requires changing the target voltage occurs, the peak value of the grid voltage is reached. This change can be detected without waiting.

The figure explaining the structure of the grid connection apparatus which concerns on embodiment. The figure explaining the processing routine started for every carrier frequency. The figure which shows the relationship between several reference voltage value parameter and AC voltage value. The figure explaining the processing routine started for every zero cross timing. The figure which shows the state of the electric power component which concerns on embodiment. The figure which shows the state of the electric power component which concerns on other embodiment. The figure which shows the state of the electric power component which concerns on a prior art example (the 1). The figure which shows the state of the electric power component which concerns on a prior art example (the 2). The figure which shows the state of the electric power component which concerns on a prior art example (the 3).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 illustrates the configuration of the grid interconnection system 10. In the figure, various distribution lines connected to the system power supply are shown. Among these, the power supply lines L1 and L2 link the inverter circuit and the system power supply (commercial power supply) through this. In addition, a load LD (not shown) is electrically connected to the power lines L1 and L2 as well as a relay RY3.

  The grid interconnection system 10 according to the present embodiment includes a distributed power source PVP, a junction box PVB, a relay RY2, a grid interconnection device 100, a single operation detection device (not shown), an appropriate signal line, and the like. Is done. In the present embodiment, the solar cell module PVP is used as the distributed power source. However, a small-scale power generation device using natural energy such as a fuel cell or a wind power generation device may be used.

  The junction box PVB combines the generated power supplied from each module of the solar cell module PVP, and outputs the supplied power in the DC state to the grid interconnection device 100. The junction box PVB is electrically connected to the input unit 101 of the grid interconnection device 100 and relays the supply power generated by the solar cell module PVP.

  The grid interconnection device 100 includes a converter circuit 110, an inverter circuit 120, a filter circuit 130, various sensors (141q, 141r, 141t), and a control circuit 150. Further, power supply lines L1 and L2 are connected to the output side of the inverter circuit 120, and in addition, signal lines are appropriately provided in the sensor unit.

  In the converter circuit 110, a series circuit including a reactor Lc1 and a diode D1 is provided on the bus line La, and an active element T1 is provided between the anode side of the diode D1 and the bus line Lb. On the cathode side of the diode D1, a smoothing capacitor C1 is connected between both bus lines so as to be in parallel with the active element T1. The converter circuit 110 repeats the operation in which the active element T1 is energized / de-energized according to the drive signal s1, and supplies electric charges to the smoothing capacitor C1 by the action of the reactor Lc1. For this reason, in the smoothing capacitor C1, the both-ends voltage in the said capacitor is maintained higher than the voltage component in supply electric power by balancing supply charge amount and discharge charge amount suitably. Hereinafter, such a state of the voltage across the smoothing capacitor C1 is referred to as a boosted voltage.

  The bus line La is provided on the anode side of the smoothing capacitor C1, and the bus line Lb is provided on the cathode side of the same element. The bus lines La and Lb are interposed between the converter circuit 110 and the inverter circuit 120 and electrically connect both circuits. Since the bus lines La and Lb are connected corresponding to the electrode terminals of the smoothing capacitor C1, the DC power is relayed from the smoothing capacitor C1 to the subsequent circuit (inverter circuit 120). Since the bus voltage (voltage value of the boosted voltage) between the bus lines La to Lb is determined by the amount of charge in the smoothing capacitor C1, the voltage value is determined according to the circuit operations of both the converter circuit 110 and the inverter circuit 120. It will be. Hereinafter, the bus lines La and Lb between the converter circuit 110 and the inverter circuit 120 may be collectively referred to as a DC link unit.

  The inverter circuit 120 includes a first semiconductor arm in which active elements T2a and T2b are connected in series, and a second semiconductor arm in which T2c and T2d are connected in series, and the plurality of semiconductor arms are connected to the bus lines La and Lb. Are connected in parallel. The contact t1 (output end) of T2a and T2b is connected to the power supply line L1 through the filter reactor, and is electrically connected to the system power supply through this. Similarly, in the power supply line L2, the contact point t2 (contact point / output end of T2c and T2d) and the system power supply are electrically connected through another filter reactor. In the inverter circuit 120, the active elements T2a to T2d switch the energized state in accordance with the drive signals sa to sd, whereby the output current Iac is pulse-width modulated and converted into a sine wave. As described above, the inverter circuit 120 converts the intermediate power output from the converter circuit 110 into AC power, and reversely flows the AC power to the system power supply.

  The above-mentioned active element refers to a power transistor that regulates the energized state, and a MOSFET or IGBT is used. In such an active element, a drive signal (for example, a PWM signal) is input to a signal terminal, and an energized current is intermittently operated at a high frequency (several kHz to several tens of kHz). The active element group in the claims is a general term for the active element T1 on the converter circuit side and the active elements T2a to T2d on the inverter circuit side.

  As shown in the figure, the control circuit 150 is provided in the grid interconnection device 100, and includes a CPU, a memory circuit, an AD conversion circuit, a clock circuit, and the like as an internal configuration. An input port provided in the control circuit 150 includes an input-side current detection signal sq that indicates a current component of the supplied power, and an output-side current detection signal that indicates the current value of the current (ie, output current) supplied to the system power supply. sr, a bus voltage detection signal st indicating the voltage value of the bus voltage, and the like are input. Further, the control circuit 150 generates the drive signals s1, sa to sd described above, and the drive signals s1, sa to sd are output from the output ports provided in the control circuit 150.

  Of the circuit configuration described above, various programs are recorded in the memory circuit, and when these programs are read into a register in the CPU, these hardware resources and software resources cooperate to construct a later-described functional unit. More specifically, in the control circuit 150 according to the present embodiment, a converter control unit 151, an inverter control unit 152, a disconnection relay control unit (not shown), and the like are constructed.

  Among these, the disconnection relay control unit receives information indicating that the system power supply is in a power failure state from an isolated operation detection device (not shown), and controls the relay RY3 to be disconnected based on this information. When the system power supply is restored, the relay RY3 is operated in series in response to this information.

  The converter control unit 151 includes an input component detection unit 151d, an MPPT control unit 151c, a parameter calculation unit 151b, a PWM signal generation unit 151a, and the like. The input component detection unit 151d creates data based on the signal sq for the current component of the supplied power (that is, the current component flowing to the reactor Lc), and stores this data in a register or memory circuit of the CPU.

  After that, the MPPT control unit 151c specifies the power value that is the maximum power point based on the VI output characteristics. In the present embodiment, a target current value serving as the maximum power point is specified using a so-called “mountain climbing method”.

  Thereafter, the parameter calculation unit 151b compares the “previous target current value” with the “current flowing to the reactor Lc”, and performs PI control so that the difference value converges to zero, thereby achieving the target value of the boost voltage. The parameter indicating is calculated.

  Thereafter, the PWM signal generation unit 151a generates a drive signal (PWM signal) s1 based on this parameter, and drives the active element T1 via a drive circuit (not shown) or the like. As described above, the converter control unit 151 controls the amount of charge applied to the smoothing capacitor C1 while monitoring the passing current of the reactor Lc.

  The inverter control unit 152 includes a power component detection unit 152f, an AC voltage acquisition unit 152e, an AC voltage value parameter setting unit 152d, a reference voltage value parameter setting unit 152c, a target bus voltage correction unit 152b, and a PWM signal generation The unit 152a and the like are functionally configured. In the present embodiment, the power component detection unit 152f, the AC voltage acquisition unit 152e, and the AC voltage value parameter setting unit 152d are incorporated in a program that defines the modulation factor calculation routine of FIG. The target bus voltage correction unit 152b corresponds to the AC voltage parameter calculation routine S21 in FIG. 2B, a program that defines a bus voltage correction determination routine, and a program that defines a bus voltage correction amount setting routine. In this embodiment, the modulation factor calculation routine, the AC voltage parameter calculation routine, and the bus voltage correction determination routine are started for each carrier cycle (the carrier frequency is set to 17 kHz).

  In the bus voltage detection process S11, the voltage across the smoothing capacitor C1 is detected based on the signal st, and data (DC detection value data) indicating the voltage across the smoothing capacitor is created in a data register or the like. Further, in the output current detection process S12, the output current Iac of the inverter circuit is detected based on the signal sr, and the electronic component is made to create data as in the above.

  In the current command value setting process S13, the amplitude of the output current is multiplied by a value corresponding to the phase of the sine wave, and this is set as the current command value. Note that the present invention is not limited to this, and an appropriate correction value may be added. In the current difference value calculation process S14, a difference value ΔI between the current command value and the output current is calculated.

  When the difference value ΔI is calculated, in the AC voltage component calculation process S15, AC voltage value data is created so that the difference value ΔI converges to zero. This AC voltage value data is determined by PI control, and when the control proceeds so that the difference value ΔI converges to zero, it is subsequently saturated to the voltage value of the system power supply. That is, the AC voltage value data in the present embodiment means that the voltage value corresponding to this is indirectly monitored without directly monitoring the voltage value of the system voltage.

  In the modulation factor calculation process S16, modulation factor value information calculated corresponding to the AC voltage value data is calculated. This modulation rate information is information updated every carrier cycle (about 0.059 msec). More specifically, the modulation factor value information calculates “MR = Vac / Vdc (ins)” using the AC voltage value data Vac and the DC detection value data Vdc (ins) when the carrier period arrives. This parameter MR is called a modulation rate, and is a parameter indicating a value fluctuation state. The modulation factor according to the present embodiment indicates the output fluctuation of the solar cell module PVP (denominator) and also expresses the fluctuation of the voltage component of the system power supply (numerator).

  When the modulation factor calculation routine ends, the AC voltage parameter calculation routine is started. In the target bus voltage value correction processing S21, if the bus voltage target value Vdc is not changed, the current target voltage value Vdc (n) is deferred as a set value. If the target value of the bus voltage needs to be changed, the changed target voltage value is set as Vdc (n + 1).

  Thereafter, in the AC voltage component parameter calculation process S22, the AC voltage component parameter is calculated using the target voltage value Vdc. The AC voltage parameter is a parameter after PI control calculated based on the difference value ΔI between the output current value and the current command value, and the target voltage value Vdc is included in the parameter. In other words, the AC voltage parameter is a parameter that reflects the fluctuation of the target voltage value Vdc, in other words, a parameter that is changed in response to the fluctuation of the solar cell module and the voltage fluctuation of the system power supply.

  When the AC voltage parameter is calculated, the parameter is input to the PWM signal generation unit 152a, and a drive signal (PWM signal) is generated there. The PWM signals sa to sd are output to the active elements T2a to T2d to control the output current Iac of the inverter circuit 120.

  In the bus voltage correction determination routine (see FIG. 2c), a reference voltage value parameter is set in advance. The reference voltage value parameter is a voltage value parameter indicating a reference waveform substantially similar to the AC voltage waveform of the system power supply. In the present embodiment, the reference voltage value parameter is calculated from reference voltage value data representing the voltage value of the reference waveform Vth (see FIG. 4) and DC detection value data. Hereinafter, this is referred to as reference modulation rate information MRth.

  In the bus voltage correction determination routine according to the present embodiment, two types of reference values are provided as reference modulation rate information MRtha and reference modulation rate information MRthb, which are respectively “MRtha = 0.97, MRthb = 0. .95 ". Thus, in the bus voltage correction determination routine, the first processing path of the process S31 → the process 32, the second processing path of the process S31 → the process 33 → the process 35, and the third processing path of the process S31 → the process 33 → the process 34. And are formed.

  When the AC modulation factor value information MR calculated for each carrier cycle is “MR> 0.97”, the first command information recording process S32 is conducted to increase the target voltage value Vdc. Command information ”is recorded in the memory circuit. In this case, the modulation rate is very high, and there is a danger that the current bus voltage is close to the voltage value of the system power supply (see FIG. 3a). Therefore, the “first command value” is set immediately when the modulation rate becomes high (at the time of the first processing path). This is to quickly avoid the approach between the bus voltage and the voltage value of the system power supply.

  On the other hand, when the AC modulation factor value information MR calculated for each carrier cycle is “MR ≦ 0.95”, the instruction is guided to the second command information recording process S35, on the condition that a predetermined time has passed. The “second command information” for decreasing the target voltage value Vdc is recorded in the memory circuit. The reason why the target voltage value Vdc is lowered is to avoid heat generation in the converter circuit 110 (see FIG. 3b). Further, in the present embodiment, in setting “second command information”, a continuation period of 500 msec is waited after switching to the second processing path. That is, the time required to give the decrease correction amount “−ΔVg” (second correction standby time) is set longer than the time required to give the increase correction amount “+ ΔVg” (first correction standby time). ing. This is because reducing the target voltage value Vdc may induce an approach to the system voltage, so this operation should be considered carefully.

  When the process is executed in the third processing path, the AC modulation rate value information MR becomes “0.97> MR> 0.95” as shown in FIG. There are no major fluctuations. If the fluctuation is in such a range, the control is continued at the currently set target voltage value Vdc without changing the target voltage value Vdc. In addition, the time count clear process S34 is for starting the count value to zero when the processing path is transferred from the second processing path to the third processing path within 500 msec and again when the processing path is transferred to the third processing path. It is.

  As described above, in the bus voltage correction determination routine, the type of the correction command, such as whether to increase, decrease, or maintain the target voltage value Vdc, is determined based on the magnitude relationship of the modulation rate. In order to realize such control, a plurality of reference modulation factor value information MRtha and MRthb provided corresponding to different modulation factors are provided.

  In the present embodiment, a bus voltage correction amount setting routine (see FIG. 4) is started every zero cross timing (every 17 msec or every 20 msec) of the system voltage. If the first command information (increase command information) is detected (step S41), an increase correction value setting process S42 is executed to determine “correction amount: + ΔVg”. If the second command information (decrease command information) is detected (S44), a decrease correction value setting process S45 is executed to determine “correction amount: −ΔVg”. When this correction amount is determined, these correction commands are initialized so that they are not erroneously reflected in the next processing (S43, S46). The absolute value of this correction amount may be changed depending on whether it is increased or decreased.

  In the present embodiment, a target voltage value Vdc larger than the peak value Vp (n) of Vac (n) is set based on the modulation factor value information. As shown in FIG. 5A, the modulation factor value information indicates a similar reference waveform Vth (n) of the AC voltage value data Vac (n), and until the time t3, the AC voltage value Vac (n ) And the target voltage value Vth (n) maintain a good relationship, so that the target voltage Vdv (n) does not change.

  Thereafter, when the time tx is reached, the AC voltage value exceeds the reference waveform Vth (n). At this time, the modulation factor MR (n) exceeds 0.97, and the target voltage value Vdc is determined by the bus voltage correction determination routine. Increase command information is set. Therefore, at the next zero cross timing t4, a new reference modulation factor MR (n + 1) and a target voltage value Vdc (n + 1) are set, and the signal generation unit 152a generates a drive signal using these.

  According to grid interconnection device 100 according to the present embodiment, since the reference value (reference modulation rate) is set using waveform data similar to the grid voltage, when an event for changing the target voltage occurs, This variation can be detected without waiting for the peak value of the system voltage to arrive.

  According to the present embodiment, since the target voltage value Vdc is changed at each zero cross timing, when the time t4 arrives, the correction amount “+ ΔVg” for the target voltage value Vdc is quickly given. Therefore, an AC voltage component parameter is calculated based on the corrected target voltage value Vdc (n + 1), and a PWM signal is generated and output based on the AC voltage component parameter. Thus, by controlling the output current Iac, the bus voltage can be controlled without approaching the AC voltage value Vac.

  Further, when the bus voltage correction amount setting routine can be started for each carrier cycle, the target voltage value Vdc can be quickly changed as the modulation rate changes (time ty) as shown in FIG. In this case, the target voltage value Vdc can be changed without waiting for the next zero-cross timing, and further contribution can be expected to suppress harmonics of the output current Iac.

  Although the present invention has been specifically described above based on the embodiments and examples, the invention described in the claims is not limited by such matters, and is based on the technical idea of the invention. Changes can be made as appropriate. For example, according to the above embodiment, the target voltage value Vdc at the time of increase is determined by “Vdc (n + 1) = Vdc (n) + ΔVg”. However, the present invention is not limited to this equation, and a proportional value may be given to Vdc (n) to calculate the next target value Vdc (n + 1).

  Further, according to the embodiment, the inverter control unit 152 performs the substantial control of the bus voltage. However, the invention according to the claims is not limited to this, and the converter controller 152 may control the bus voltage.

  Further, according to the present embodiment, the result value of the PI control based on the current command value and the output current is “AC voltage value data”. However, the “AC voltage value data” described in the claims is not limited to this, and may be data created based on a voltage signal received from an AC voltage detection sensor.

  Furthermore, according to the above embodiment, the modulation rate is set as the AC voltage value parameter, and the change of the bus voltage (sunlight level) is compared by comparing this modulation rate with the reference modulation rate (threshold on the sine wave). Change or system voltage change). However, the technical idea described in the scope of claims is not limited to this, and various parameters that are similar to the system voltage waveform can be applied.

  As an example, in the invention described in any one of claims 7 to 11 in the claims, it is proposed to use an AC voltage value as a parameter as it is and to give a sinusoidal threshold value thereto. doing.

  That is, in the inverter control unit 152, an AC voltage value acquisition unit that creates AC voltage value data corresponding to the voltage value of the system power supply, and a reference voltage that represents a voltage value of a reference waveform that is substantially similar to the AC voltage waveform of the system power supply A reference voltage value data setting unit in which value data is set, a target bus voltage correction unit that corrects the target value of the bus voltage based on the magnitude relationship between the AC voltage value data and the reference voltage value data, and the corrected target value Thus, the function is constructed with the signal generation unit that generates the drive signal.

  As pointed out in “Problems to be Solved by the Invention”, in the grid interconnection device, the voltage value Vdc (ins) at the DC link portion shows a large periodic fluctuation in accordance with the deterioration of the smoothing capacitor (electrolytic capacitor). It will be accompanied. In this case, in the grid interconnection device according to the conventional example, a situation is formed in which the voltage value Vdc (ins) at the DC link portion is temporarily lower than the voltage value Vac of the grid power supply. As a result, the quality of the output current caused by the reverse flow of the current will be reduced.

  On the other hand, in the present invention, the target voltage value Vdc of the DC link unit is quickly corrected while monitoring the modulation rate, so that the voltage value Vdc (ins) at the DC link unit is lower than the voltage value Vac of the system power supply. It is controlled so as to rise before, and the quality of the output current reversely flowed from the grid interconnection device is maintained.

  10 grid interconnection system, 100 grid interconnection device, PVP solar cell module, PVB junction box, RY2 to RY3 relay, 110 converter circuit, 120 inverter circuit, 130 filter circuit, 150 control circuit, 151 converter control unit, 152 inverter control Unit, 152e AC voltage value acquisition unit, 152d AC voltage parameter setting unit, 152c reference voltage parameter setting unit, 152b target bus voltage correction unit, 152a PWM signal generation unit, MR modulation rate value information, Vdc DC detection value data, Vth reference Waveform data.

Claims (11)

A converter circuit that boosts the power supplied from a distributed power source; an inverter circuit that converts DC power output from the converter circuit into AC power and reversely flows the AC power to a system power source; and The DC power is relayed to the inverter circuit and the bus voltage changes according to the operation of both circuits, and the drive signal to be input to each of the converter circuit and the active element group provided in the inverter circuit is generated. A control circuit,
The control circuit includes an AC voltage value acquisition unit that generates AC voltage value data corresponding to the voltage value of the system power supply, and an AC voltage value parameter setting unit that sets an AC voltage value parameter corresponding to the AC voltage value data. A reference voltage value parameter setting unit for setting a reference voltage value parameter corresponding to a voltage value of a substantially similar reference waveform with respect to the AC voltage waveform of the system power supply, and the magnitude of the AC voltage value parameter and the reference voltage value parameter A system in which a target bus voltage correction unit that corrects a target value of the bus voltage based on a relationship and a signal generation unit that generates the drive signal using the corrected target value are constructed. Interconnection device. The AC voltage value parameter is AC modulation rate value information calculated from the AC voltage value data and the DC detection value data of the bus voltage,
The reference voltage value parameter is reference modulation factor value information calculated from reference voltage value data representing the voltage value of the reference waveform and DC detection value data of the bus voltage. The grid interconnection device described.   The target bus voltage correction unit compares the AC modulation factor value information and the reference modulation factor value information to determine a correction command type and a bus voltage correction determination program based on the correction command. The grid interconnection apparatus according to claim 2, wherein a bus voltage correction amount setting program for determining a correction amount to be given to the value is started.   The grid interconnection apparatus according to claim 2 or 3, wherein the reference modulation factor value information includes a plurality of reference modulation factor value information provided corresponding to different modulation factors.   The plurality of reference modulation factor value information includes first reference modulation factor value information used when setting increase command information indicating whether or not to increase the correction amount, and whether or not to decrease the correction amount. 5. The grid interconnection device according to claim 4, further comprising second reference modulation factor value information used when setting the reduction command information.   In the bus voltage correction determination program, the second correction standby time required to decrease the correction amount is set longer than the first correction standby time required to increase the correction amount. The grid interconnection device according to claim 5. A converter circuit that boosts the power supplied from a distributed power source; an inverter circuit that converts DC power output from the converter circuit into AC power and reversely flows the AC power to a system power source; and The DC power is relayed to the inverter circuit and the bus voltage changes according to the operation of both circuits, and the drive signal to be input to each of the converter circuit and the active element group provided in the inverter circuit is generated. A control circuit,
The control circuit includes an AC voltage value acquisition unit that generates AC voltage value data corresponding to the voltage value of the system power supply, and reference voltage value data that represents a voltage value of a reference waveform that is substantially similar to the AC voltage waveform of the system power supply. A reference voltage value data setting unit in which is set, a target bus voltage correction unit that corrects the target value of the bus voltage based on the magnitude relationship between the AC voltage value data and the reference voltage value data, and the corrected target value And a signal generating unit that generates the drive signal using a power system.   The target bus voltage correction unit compares the AC voltage value data and the reference voltage value data to determine a correction command type, and sets the bus voltage target value based on the correction command. The system interconnection apparatus according to claim 7, wherein a bus voltage correction amount setting program for determining a correction amount to be applied is started.   The grid interconnection device according to claim 7 or 8, wherein the reference voltage value data is constituted by a plurality of reference voltage value data provided corresponding to different ratios.   The plurality of reference voltage value data includes first reference voltage value data used for setting increase command information for determining whether to increase the correction amount, and a decrease command for determining whether to decrease the correction amount. The grid interconnection device according to claim 9, further comprising: second reference voltage value data used when setting information.   In the bus voltage correction determination program, the second correction standby time required to decrease the correction amount is set longer than the first correction standby time required to increase the correction amount. The grid interconnection apparatus according to claim 10.

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