JP2014117086A - System interconnection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system interconnection system capable of discharging electric charge of a filter capacitor without additional circuit configuration.SOLUTION: When a first command signal is outputted from a control circuit 130, transistors T2a, T2c of a high-side transistor group Tx are brought into a conducted state (ON state) and transistors T2b, T2c of a low-side transistor group Ty are brought into non-conducted state (OFF state). Thus, after parallel-off from a system power source, switching control is performed on an inverter circuit 120 in accordance with the first command signal, such that a discharging route of electric charge of a filter capacitor Cf is formed by the inverter circuit. Therefore, a system interconnection system 10 is capable of discharging the electric charge of the filter capacitor in simple configuration without additionally providing circuits.

Description

  The present invention relates to a grid interconnection system, and more particularly to a preferable operation when disconnected from a grid power supply.

  The grid interconnection system is interposed between the distributed power source and the system power source, and is appropriately connected to these power sources via a power line. This grid interconnection system includes a power conditioner, a filter circuit provided between the power conditioner and the system power supply, a relay for disconnecting from the system power supply, and the like. Then, normally, the generated power is supplied from the distributed power source to the system power source, and is disconnected from the system power source in the event of a power failure of the system power source.

  The disconnecting relay automatically returns to the original interconnected state after a certain period of time specified by the power company has elapsed after the system power supply has recovered normally. At this time, when the polarity of the filter capacitor and the polarity of the system power supply at the time of return are opposite, an inrush current equivalent to twice flows in the filter capacitor compared to the case where the capacitor is connected from the zero charge state. This may cause deterioration of the filter capacitor and disconnection relay.

  In order to avoid such a problem, for example, if a technique such as Japanese Patent Laid-Open No. 2001-186664 (Patent Document 1) or Japanese Patent Laid-Open No. 2003-169474 (Patent Document 2) is used, an appropriate circuit is separately provided in the filter circuit. It is possible to protect the elements such as the filter capacitor or the relay circuit by discharging the charge of the filter capacitor after the disconnection operation.

JP 2001-186664 A JP 2003-169474 A

  However, according to the technique of Patent Document 1 or Patent Document 2, since a circuit for discharging electric charge from the filter capacitor is required separately, the circuit configuration of such a system becomes complicated and the cost of the apparatus increases.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a system interconnection system capable of discharging the charge of a filter capacitor without an additional circuit configuration.

In order to solve the above problems, the first invention adopts the following power conditioner configuration. That is, a circuit having a plurality of semiconductor arms in which power transistors are connected in series, an inverter circuit that converts supply power based on a distributed power source into AC power, a filter reactor, and output power of the inverter circuit to a system power source A plurality of power supply lines connected to allow reverse power flow, a filter capacitor having one end connected to one of the power supply lines and the other end connected to the other of the power supply lines, and the filter capacitor of the power supply lines and the system power supply In a grid interconnection system comprising: an electric circuit interruption unit that is provided between and disconnecting from and disconnecting from the grid power source; and a control circuit that commands the operation of the power transistor,
After the circuit breaker is disconnected, the control circuit causes the high-side transistor group including the high-side power transistors provided in each of the semiconductor arms to be in a conductive state, and the semiconductor arm A first command signal that causes a low-side transistor group including a low-side power transistor provided in each of the transistors to be in a non-conductive state is output.

In the second invention, the following power conditioner configuration is adopted. That is, a circuit having a plurality of semiconductor arms in which power transistors are connected in series, an inverter circuit that converts supply power based on a distributed power source into AC power, a filter reactor, and output power of the inverter circuit to a system power source A plurality of power supply lines connected to allow reverse power flow, a filter capacitor having one end connected to one of the power supply lines and the other end connected to the other of the power supply lines, and the filter capacitor of the power supply lines and the system power supply In a grid interconnection system comprising: an electric circuit interruption unit that is provided between and disconnecting from and disconnecting from the grid power source; and a control circuit that commands the operation of the power transistor,
After the circuit breaker is disconnected, the control circuit causes the high-side transistor group including the high-side power transistors provided in each of the semiconductor arms to be in a non-conductive state, and the semiconductor It is assumed that a second command signal for making a low-side transistor group composed of low-side power transistors provided in each arm conductive is output.

In the third invention, the following power conditioner configuration is adopted. That is, a circuit having a plurality of semiconductor arms in which power transistors are connected in series, an inverter circuit that converts supply power based on a distributed power source into AC power, a filter reactor, and output power of the inverter circuit to a system power source A plurality of power supply lines connected to allow reverse power flow, a filter capacitor having one end connected to one of the power supply lines and the other end connected to the other of the power supply lines, and the filter capacitor of the power supply lines and the system power supply In a grid interconnection system comprising: an electric circuit interruption unit that is provided between and disconnecting from and disconnecting from the grid power source; and a control circuit that commands the operation of the power transistor,
After the circuit breaker is disconnected, the control circuit causes the high-side transistor group including the high-side power transistors provided in each of the semiconductor arms to be in a conductive state, and the semiconductor arm A first command signal for making a low-side transistor group composed of a low-side power transistor provided in each of the semiconductor devices non-conductive, and a high-side transistor group composed of a high-side power transistor provided in each of the semiconductor arms And a second command signal for alternately turning on a low-side transistor group composed of low-side power transistors provided in each of the semiconductor arms.

  According to the grid interconnection system according to the present invention, the inverter circuit is controlled after disconnecting from the system power supply, so that the discharge path of the charge of the filter capacitor is formed in the inverter circuit. For this reason, the grid interconnection system can discharge the charge of the filter capacitor with a simple configuration without separately providing a circuit.

The figure explaining the structure of a grid connection system. The figure explaining a high side transistor group and a low side transistor group. The figure explaining the discharge path of the electric charge of a filter capacitor (the 1). FIG. 2 is a diagram for explaining a discharge path of charge of a filter capacitor (No. 2).

  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 electrically connect the inverter of the grid interconnection system 10 and the system power supply (commercial power supply) via a transformer (not shown). The power supply lines Lp and Ln are connected to the branch points tp and tn provided in the power supply lines L1 and L2. In addition, an appropriate load LD1 is electrically connected to the power supply lines Lp and Ln together with a breaker (relay RY1) interposed therebetween. A plurality of such loads LD1 may be connected.

  The grid interconnection system 10 according to the present embodiment includes a solar cell module PVP (distributed power source in claims), a connection box PVB, a power conditioner unit 100, and power supply lines L1 and L2 connected thereto. , The disconnection relay RY3 (electric circuit breaker), the isolated operation detection device 150, and an appropriate signal line.

  The junction box PVB combines the generated power supplied from each module of the solar cell module PVP, and outputs this as first DC power. The junction box PVB is electrically connected to the input unit 101 of the power conditioner unit 100 and applies the generated power supplied from the solar cell module PVP to the power generation unit input unit 101.

  The power conditioner unit 100 includes a boost converter 110, an inverter circuit 120, a control circuit 130, and a filter circuit 140, and further includes an input unit 101, an output unit 102, power supply lines L1 and L2, and appropriate signal lines. Is provided.

  Boost converter 110 functions to boost the input voltage and follow the maximum power. This maximum power follow-up control refers to control by a so-called MPPT (Maximum Power Point Tracker) method. Note that the MPPT method is a well-known technique in, for example, Japanese Patent Application Laid-Open No. 2011-101455, and the description thereof is omitted. As shown in the figure, in the boost converter 110, a reactor Lc1 and a diode D1 are inserted into a power supply line La, and a power transistor T1 is connected between La and Lb of the power supply line. On the cathode side of the diode D1, a smoothing capacitor C1a is connected in parallel to the power transistor T1. In step-up converter 110, first DC power is input via power generation input terminal 101, boosts this, and outputs the boosted voltage to inverter 120 as second DC power.

  The first DC power is indirectly supplied via the junction box PVB. However, when the solar cell module PVP is used as the power source, the first DC power is supplied based on the distributed power source. The Further, the second DC power is indirectly supplied via the preceding circuit, such as “junction box PVB” → “boost converter 110”, but this also uses the solar cell module PVP as a power source. In this case, the power is supplied based on the distributed power source. Thus, the supplied power based on the distributed power source does not ask for a change state in the middle of the power.

  The inverter 120 includes a first semiconductor arm in which power transistors T2a and T2b are connected in series, and a second semiconductor arm in which T2c and T2d are connected in series. The plurality of semiconductor arms are connected to power supply 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 Lf, and is electrically connected to the system power supply through this. Similarly, in the power supply line L2, the contact t2 (the contact / output end of T2c and T2d) and the system power supply are electrically connected through another filter reactor Lf. When the power transistors T2a to T2d are driven, the inverter circuit 120 converts the input power into a sine wave by performing pulse width modulation. That is, the inverter circuit 120 converts the second DC power input from the boost converter 110 into AC power. Since the power supply lines L1 and L2 are connected as described above, the output power (AC power) of the inverter circuit 120 is caused to flow backward to the system power supply (power is supplied to the system power supply).

  The filter circuit 140 is provided with a filter reactor Lf in each of the power supply lines L1 and L2, and is responsible for current smoothing. Further, a filter capacitor Cf is provided between the power supply lines L1 and L2, one end of which is connected to the power supply line L1, and the other end is connected to the power supply line L2. As described above, the filter circuit 140 takes measures against EMI (Electric Magnetic Interference) by the filter reactor Lf and the filter capacitor Cf.

  The disconnecting relay RY3 (electric circuit interruption unit) is provided in each of the power supply lines L1 and L2, and the setting section is between the filter capacitor Cf and the system power supply. The disconnecting relay RY3 is switched to a conducting state or a non-conducting state according to the input signal s3, whereby the connection state between the power conditioner unit 100 and the system power supply is changed to a disconnecting state or a connected state (conducting state). ). Thus, when the disconnection relay RY3 is disconnected, the charge of the filter capacitor Cf is not discharged toward the system power supply.

  The isolated operation detection device 150 incorporates a voltage detection unit 151 and a power failure determination unit 152. Among these, the voltage detection part 151 detects the both-ends voltage of a system power supply, and the power failure determination part 152 determines whether it is a power failure state based on the said detection voltage. And if the determination result that it is a power failure is obtained, the power failure determination part 152 will output the power failure detection signal s2 showing this.

  As shown in the figure, the control circuit 130 is provided in the power conditioner unit 100, and includes a CPU, a memory circuit, an AD conversion circuit, a clock circuit, and the like as an internal configuration. Further, a power failure detection signal s2, a voltage value signal that detects the voltage across the smoothing capacitor C1, a current value signal that detects the output current of the inverter circuit, and the like are input to the input port provided in the control circuit 130. The

  In addition, various programs are recorded in the memory circuit, and these programs are fetched to a register in the CPU, whereby these hardware resources and software resources cooperate to construct a later-described functional process. As shown in the figure, in the control circuit 130 according to the present embodiment, a converter control processing unit 131, an inverter control processing unit 132, and a disconnection relay control processing unit 133 are constructed.

  Among these, the converter control processing unit 131 detects the current of the reactor Lc1, and sets the PWM signal s1 to be given to the power transistor T1 so that the current converges to the target current. This target current is a current value obtained as a result of processing by the MPPT method, and is a value that causes the output power to follow the maximum value.

  The inverter control processing unit 132 includes an output mode processing unit 132a and a disconnection mode processing unit 132b. Among these, the output mode processing unit 132a functions while the disconnecting relay RY3 is in the connected state. The output mode 132a detects the output current from the inverter circuit 120, introduces a difference value between the detected current and the required current to the proportional control calculation unit, and calculates command signals sa to sd (PWM signals) to be given to the transistors. To do. Here, the command signal sa is output to T2a, the command signal sb is output to T2b, the command signal sc is output to T2c, and the command signal sd is output to T2d. The requested current is sine waveform information set in synchronization with the cycle of the system power supply, and the output mode processing unit 132a instructs the power transistors T2a to T2d to operate, so that the on-duty periods of T2a and T2d , T2b and T2c are appropriately set, and the output current is shaped to correspond to the sine waveform of the system power supply.

  When the power failure detection signal s2 is input from the isolated operation detection device 150, the disconnection relay control processing unit 133 outputs the signal s3 and causes the disconnection relay RY3 to be disconnected. The disconnection relay control processing unit 133 gives the information indicating that the disconnection has been performed to the inverter control processing unit 132, thereby stopping the operation of the inverter circuit 120 based on the output mode processing unit 132a.

  After the disconnecting relay RY3 is brought into the disconnected state, the inverter control processing unit 132 causes the disconnecting mode processing unit 132b to function. In the disconnection mode processing unit 132b, the same command signal is given to the power transistor on the common side provided in each of the semiconductor arms, the power transistor group on one common side is turned on, and the power transistor group on the other common side is turned on. The power transistor group is turned off.

  In the present embodiment, as shown in FIG. 2, a group of combinations of high-side power transistors T2a and T2c is referred to as a high-side transistor group Tx. A group of combinations of the low-side power transistors T2b and T2d is referred to as a low-side transistor group Ty.

  Hereinafter, the variation of the operation of the inverter circuit 120 after the disconnection will be described with reference to the first to third embodiments.

  After the disconnection relay RY3 is switched to the disconnection state, the disconnection mode processing unit 132b according to the present embodiment receives a command signal (sa, sb, sc, sd) = (ON, OFF, ON, OFF). The driving states of the high side transistor group Tx and the low side transistor group Ty are set. Hereinafter, the combination state of the command signals is referred to as a first command signal.

  As described above, when the first command signal is output from the control circuit 130, as shown in FIG. 3, each of the high-side transistor groups Tx T2a and T2c is turned on (on state), and the low-side transistor group Each of Ty T2b and T2d is turned off (off state). The conduction state refers to a state in which a passing current flows between the collector and the emitter of the power transistor.

  As shown in the figure, the charge Q of the filter capacitor Cf causes a discharge current to flow into the inverter because the disconnecting relay RY3 is in the disconnected state. For example, when the electrode plate on the L1 side of the filter capacitor Cf has a positive charge (FIG. 3a), this charge is discharged, and then passes through the power supply line L1, the power transistor T2a, the power transistor T2c, and the power supply line L2. Discharge current is generated. Further, when the electrode plate on the L2 side of the filter capacitor Cf has a positive charge (FIG. 3b), this charge is discharged, and then passes through the power supply line L2, the power transistor T2c, the power transistor T2a, and the power supply line L1. Discharge current is generated.

  In this way, since the charge Q between the electrode plates decreases (or disappears) due to the discharge, it is possible to avoid a situation in which the polarity of the filter capacitor and the polarity of the system power supply are reversed when reconnected. According to this, the maximum of the inrush current that can be assumed is about half that of the reverse polarity, and the actual inrush current at the time of reconnection is suppressed to a current value lower than this. In this way, the filter capacitor Cf suppresses the inrush current generated at the time of reconnection and protects the capacitor.

  Further, according to the grid interconnection system 10 according to the present embodiment, after disconnecting from the system power supply, the inverter circuit 120 is switching-controlled by the first command signal, so that the discharge path of the charge of the filter capacitor Cf is the inverter circuit. To form. Therefore, the grid interconnection system 10 can discharge the charge of the filter capacitor with a simple configuration without separately providing a circuit. In such a scene, the filter reactor Lf inserted in the discharge path functions to suppress the current value of the discharge current.

  After the disconnection relay RY3 is switched to the disconnection state, the disconnection mode processing unit 132b according to the present embodiment receives a command signal (sa, sb, sc, sd) = (OFF, ON, OFF, ON). The driving states of the high side transistor group Tx and the low side transistor Ty are set. Hereinafter, the combination state of the command signals is referred to as a second command signal.

  In this way, when the second command signal is output from the control circuit 130, as shown in FIG. 4, each of the high-side transistor group Tx T2a and T2c is turned off (off state), and the low-side transistor Each of T2b and T2d of group Ty is turned on (on state).

  Even in this embodiment, a discharge path is formed in the inverter circuit as follows. For example, when the electrode plate on the L1 side of the filter capacitor Cf is positively charged (FIG. 4a), a discharge current is generated via the power line L1, the power transistor T2b, the power transistor T2d, and the power line L2. When the electrode plate on the L2 side of the filter capacitor Cf is positively charged (FIG. 4b), a discharge current is generated via the power supply line L2, the power transistor T2d, the power transistor T2b, and the power supply line L1.

  Thus, even in the present embodiment, since the discharge path is formed in the inverter circuit, it goes without saying that the same effects as those of the first embodiment can be obtained.

  The control circuit 130 according to the present embodiment outputs the above-described first command signal and second command signal so as to be switched alternately (third command signal). Specifically, switching is preferably performed at intervals of several milliseconds to several seconds.

  When such a signal (third command signal) is given to the inverter circuit 120, “each of the high-side transistor group Tx is in an on state and each of the low-side transistor group Ty is in an off state (first state). , And “each of the high-side transistor group Tx is in an off state and each of the low-side transistor group Ty is in an on state (second state)” are switched at predetermined intervals.

  In this case, in the discharge path, a scene passing through the high side transistor group Tx and a scene passing through the low side transistor group Ty are alternately formed. The reason for performing such an operation is to balance the stress of the transistors.

  For this reason, the disconnection mode processing unit 132b according to the present embodiment can use the discharge path advantageous for discharge for a part of the process by setting both discharge paths. Moreover, repeating such a switching operation in a short time also has an advantage that heat stress is easily balanced.

  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, in the embodiment, a solar cell module is used as a distributed power source. However, the meaning of the term “distributed power source” is not limited to this, but extends to equipment that can generate power using natural energy, such as a fuel cell, a wind power generator, and a small-scale hydroelectric generator. When such a distributed power source is used, it is necessary to appropriately replace the configuration and control of the converter incorporated in the power conditioner according to the nature of the power source.

  DESCRIPTION OF SYMBOLS 10 Electric power generation system, 12 Current sensor, PVP solar cell module, PVB connection box, RY1-RY3 relay, LD1 load, 100 system linkage system, 101 Power generation part input part, 102 Output part, 103 Storage battery input part, 110 PFC converter , 120 inverter, 130 control circuit, 140 filter circuit.

Claims (3)

A circuit having a plurality of semiconductor arms in which power transistors are connected in series, an inverter circuit that converts supply power based on a distributed power source into AC power, a filter reactor, and a reverse power flow from the output power of the inverter circuit to a system power source A plurality of power supply lines to be connected, a filter capacitor having one end connected to one of the power supply lines and the other end connected to the other of the power supply lines, and the filter capacitor of the power supply line and the system power supply. In the grid interconnection system comprising:
After the circuit breaker is disconnected,
The control circuit causes a high-side transistor group including high-side power transistors provided in each of the semiconductor arms to be in a conductive state, and includes a low-side power transistor provided in each of the semiconductor arms. A system interconnection system, wherein a first command signal for causing a low-side transistor group to be in a non-conductive state is output. A circuit having a plurality of semiconductor arms in which power transistors are connected in series, an inverter circuit that converts supply power based on a distributed power source into AC power, a filter reactor, and a reverse power flow from the output power of the inverter circuit to a system power source A plurality of power supply lines to be connected, a filter capacitor having one end connected to one of the power supply lines and the other end connected to the other of the power supply lines, and the filter capacitor of the power supply line and the system power supply. In the grid interconnection system comprising:
After the circuit breaker is disconnected,
The control circuit causes a high-side transistor group including a high-side power transistor provided in each of the semiconductor arms to be in a non-conductive state, and includes a low-side power transistor provided in each of the semiconductor arms. A grid interconnection system, characterized in that a second command signal for causing a low-side transistor group to be in a conductive state is output. A circuit having a plurality of semiconductor arms in which power transistors are connected in series, an inverter circuit that converts supply power based on a distributed power source into AC power, a filter reactor, and a reverse power flow from the output power of the inverter circuit to a system power source A plurality of power supply lines to be connected, a filter capacitor having one end connected to one of the power supply lines and the other end connected to the other of the power supply lines, and the filter capacitor of the power supply line and the system power supply. In the grid interconnection system comprising:
After the circuit breaker is disconnected,
The control circuit includes:
The high-side transistor group composed of the high-side power transistor provided in each of the semiconductor arms is made conductive, and the low-side transistor group composed of the low-side power transistor provided in each of the semiconductor arms is non-conductive. A first command signal to be turned on;
A high-side transistor group composed of high-side power transistors provided in each of the semiconductor arms is made non-conductive, and a low-side transistor group composed of low-side power transistors provided in each of the semiconductor arms is A grid interconnection system characterized by alternately outputting a second command signal to be in a conductive state.

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