JP5938068B2 - Self-sustained operation control device for distributed power source, power conditioner, and self-sustained operation control method for distributed power source - Google Patents

Description

  The present invention relates to a self-sustained operation control device for a distributed power source, a power conditioner, and a self-sustained operation control method for a distributed power source, and more particularly, an inverter that converts DC generated power into AC power, and an LC that removes harmonic components from the inverter output. A distributed power supply self-sustained operation control device configured to include a filter and configured to supply power to the self-sustained system when the system power supply drops below a predetermined voltage, a power conditioner incorporating the self-sustained operation control device, and a distributed power supply The present invention relates to a self-sustaining operation control method.

  A distributed power source such as a solar cell or a fuel cell includes a power conditioner that converts a frequency and a voltage into AC power so as to be compatible with the power system in order to be used in conjunction with system power.

  The power conditioner includes a DC / DC converter that adjusts a DC voltage generated by a distributed power source to a predetermined DC voltage value, an inverter that converts DC power output from the DC / DC converter into AC power, An LC filter that removes high-frequency components from the output is provided.

  A ground fault or short-circuit accident occurs in the distribution line where the distributed power source is connected to the grid, or power transmission from the substation to the distribution line has stopped due to a planned power failure, etc. In this case, the distributed power source is disconnected from the distribution line by the control unit of the distributed power source in order to prevent the influence on the operation of the division switch and to ensure the safety of the work of the distribution line.

  Then, AC power is controlled from the power conditioner to the independent system separated from the system power source by the control device of the distributed power source, or to the independent system independent from the system power source.

  The control device for the distributed power source includes a current control block that controls the inverter so that an alternating current synchronized with the phase of the system voltage is output from the inverter during grid connection, and a predetermined level statutory for the independent system when disconnected. A voltage control block for controlling the inverter so that a voltage is output is provided. The legally prescribed voltage levels are stipulated in Article 26 of the Electricity Business Act and Article 44 of the Enforcement Regulations of the Act, and are intended for low voltage consumers, 101 ± 6V for standard voltage 100V, Voltage within 202 ± 20V.

  Patent Document 1 discloses an inverter device for a distributed power source for suppressing fluctuations in the output voltage of an inverter device caused by load fluctuations within a predetermined allowable range.

  The inverter device includes: a first determination circuit that determines an output voltage set value by stepwise switching so that the inverter output voltage is within an allowable range based on detection of load current; and an inverter based on detection of load voltage It has a second determination circuit that determines the output voltage setting value by stepwise switching so that the output voltage falls within the allowable range. When the system is connected, the first determination circuit sets the output voltage by detecting the load current. The value is updated so that the output voltage setting value is maintained from the time of the occurrence of a system power failure to the disconnection of the interconnection switch. After the disconnection of the interconnection switch, the output voltage is detected by detecting the load voltage in the second determination circuit. A first determination circuit that enters a standby state for updating a set value, sends an output voltage command based on an output voltage set value based on load current detection after switching from the current control mode to the voltage control mode. , And a voltage control circuit to switch to the second decision circuit for delivering an output voltage command based on the output voltage set value due to the detection of the load voltage.

  In Patent Document 2, in order to suppress a rush current generated in a load connected to a self-supporting system and to ensure a stable self-sustaining operation, a rush current due to a load connected to the self-supporting system is smaller than a predetermined current value. There has been disclosed a power conditioner including a current suppressing circuit that limits the current.

JP 2012-120285 A JP-A-10-31540

  However, the inverter device for a distributed power source disclosed in Patent Document 1 needs to be provided with a dedicated load current sensor for measuring the load current, which increases the component cost and construction cost including the peripheral circuit of the current sensor. There was a problem.

  Further, the power conditioner disclosed in Patent Document 2 also includes a dedicated current suppression circuit for suppressing the inrush current, and it is necessary to incorporate a complicated control algorithm corresponding to the current suppression circuit, resulting in increased component costs. There was a problem.

  In view of the above-described problems, the object of the present invention can be controlled to a stable output voltage without providing a sensor for detecting a load current and without providing special parts even in a situation where an inrush current occurs. It is in providing a self-sustained operation control device, a power conditioner, and a self-sustained operation control method for a distributed power source.

In order to achieve the above object, a first characteristic configuration of a self-sustained operation control device for a distributed power source according to the present invention converts DC generated power into AC power as described in claim 1 of the claims. A self-sustained operation control device for a distributed power source comprising an inverter and an LC filter that removes harmonic components from the output of the inverter, and configured to be able to supply power to a self-sustained system when the system power source drops below a predetermined voltage, comprising a load current estimating unit for estimating a load current i _load supplied to the self-supporting system on the basis of the output voltage e _sd of the LC filter and the output current i _inv of the inverter, the output voltage e _sd and the load current i Based on _Load , feedback control is performed so that the target voltage e ^* _sd is output from the inverter.

The self-sustained operation control device is disconnected when the system power supply falls below a predetermined voltage, and the output current i _{inv of the} inverter and the output of the LC filter are output by the load current estimating unit so as to output an AC voltage in a predetermined voltage range to the self-supporting system. The voltage e _sd is detected, the load current i _Load supplied to the independent system is estimated based on the detected values, and the target voltage e ^* _{sd is} output from the inverter based on the detected output voltage e _sd and the estimated load current i _Load. Therefore, it is not necessary to provide a current sensor for detecting the load current, and it is possible to reduce the component cost.

According to the second characteristic configuration, as described in claim 2, in addition to the first characteristic configuration described above, the target of the inverter is maintained so that the output voltage e _sd is maintained at a predetermined target voltage e ^* _sd. a voltage control unit for feedback control of the current ⁱ _{* inv,} wherein as said target voltage ^e _{* sd} from the inverter on the basis of the target current ⁱ _{* inv} and the output current _{i inv} and the load current _{i load} is output The current control unit includes a current control unit that feedback-controls the duty ratio u ^* _d of the inverter.

In order to maintain the output voltage _esd at the target voltage e ^* _sd by the voltage control unit, the target current i ^* _{inv of the} inverter is calculated by, for example, PID control and input to the current control unit, and the target current i ^* _inv by the current control unit an output from the inverter on the basis of the current _{i inv} and the load current _{i load} as target voltage ^e _{* sd} is output, for example, by PID control duty ratio ^u _{* d} of the inverter is calculated, the inverter in the duty ratio ^u _{* d} Is controlled, the output voltage _esd is controlled to be stable even when the current flowing through the load connected to the independent system fluctuates.

In the third feature configuration, as described in the third aspect, in addition to the first or second feature configuration described above, the load current estimation unit may _{calculate the} output current i _inv and the output voltage _esd . The load current i _Load is calculated by estimating the branch current _ic flowing in the LC filter capacitor based on the output current i _inv and subtracting the branch current _ic from the output current i _inv. .

Based on the output current i _{inv of the} inverter and the output voltage _esd of the LC filter, the branch current _ic flowing through the capacitor of the LC filter is estimated, and the load current i _Load is calculated by subtracting the branch current _ic from the output current i _inv. Is done.

  The characteristic configuration of the power conditioner according to the present invention includes an inverter that converts DC generated power into AC power, and an LC filter that removes harmonic components from the output of the inverter. The output voltage of the inverter is controlled by a self-sustained operation control device for a distributed power supply having a configuration.

The first characteristic configuration of the self-sustained operation control method for a distributed power source according to the present invention is an inverter that converts DC generated power into AC power and removes harmonic components from the output of the inverter as described in claim 5. A self-sustained operation control method for a distributed power source comprising an LC filter and configured to be able to supply power to a self-sustained system when the system power source drops below a predetermined voltage, the output current i _{inv of the} inverter and the output voltage of the LC filter estimating the load current _{i load} supplied to the self-supporting system based on e _sd, feedback control so that the target voltage ^e _{* sd} from the inverter on the basis of said output voltage _{e sd} to the load current _{i load} is output There is in point to do.

In the second feature configuration, in addition to the first feature configuration described above, the target of the inverter is maintained so as to maintain the output voltage e _sd at a predetermined target voltage e ^* _sd. A voltage control step for feedback-controlling the current i ^* _inv , a load current estimation step for estimating a load current _iLoad supplied to the independent system based on the output current _iinv and the output voltage _esd , and the target current i ^* _inv and on the basis of the output current _{i inv} and the load current _{i load} a current control step of feedback control of the duty ratio ^u _{* d} of the inverter so that the target voltage ^e _{* sd} from the inverter is outputted There is in point.

In the third feature configuration, in addition to the first or second feature configuration described above, the load current i _Load is expressed by the output current i _inv and the output voltage _esd . based wherein estimating the branch current i _c flowing to the capacitor of the LC filter, from the output current i _inv a point which is estimated by subtracting the branch current i _c.

  As described above, according to the present invention, a distributed type that can be controlled to a stable output voltage without providing a sensor for detecting a load current and without providing special parts even in a situation where an inrush current occurs. A self-sustained operation control device for a power supply, a power conditioner, and a self-sustained operation control method for a distributed power supply can be provided.

Circuit block configuration diagram of a distributed power source to which a self-sustained operation control device for the distributed power source is applied Explanatory diagram of connection relationship between system power supply, distribution board and distributed power supply Explanatory drawing of the estimation process of the load current performed by the autonomous operation control device Illustration of the autonomous operation control algorithm Parameter explanatory diagram of confirmation experiment of autonomous operation control algorithm Explanatory diagram of experimental results of autonomous operation control algorithm

  Hereinafter, a self-sustained operation control device for a distributed power source according to the present invention, a power conditioner incorporated in the self-sustained operation control device, and a self-sustained operation control method for a distributed power source will be described with reference to the drawings.

  FIG. 1 shows a solar power generation device 1 that is an example of a distributed power source. The solar power generation device 1 includes a solar cell panel SP and a power conditioner PC to which the solar cell panel SP is connected. The DC power generated by the solar cell panel SP is supplied to the power conditioner PC via the DC circuit breaker 6 and the surge absorber 7.

The power conditioner PC converts the DC voltage generated by the solar cell panel SP to a predetermined DC link voltage _Vdc and converts the boosted DC link voltage _Vdc into a predetermined AC voltage. An inverter 3, an LC filter 4 that removes harmonics from the AC voltage output from the inverter 3, a DC / DC converter 2, a control device 5 that controls the inverter 3, and the like are provided.

  The AC power converted by the power conditioner PC is configured to be connected to the system power supply 100 via the surge absorber 8 and the system relay Ry1, and when disconnected from the system power supply 100, the power is supplied to the independent load 20 via the independent relay Ry2. Connected as possible.

  The control device 5 of the power conditioner PC includes a converter control unit 5a that controls a boost switch of the DC / DC converter 2 and an inverter control unit 5b that controls a switch that forms a bridge of the inverter 3, and each includes a microcomputer and a control unit 5b. The peripheral circuit includes a memory element, an input / output element, and the like.

  The converter control unit 5a monitors the input voltage, input current, and output voltage to the DC / DC converter 2 and performs MPPT control to operate the solar panel SP at the maximum power point, and boosts it to a predetermined output voltage. Control.

  The inverter control unit 5b includes a current control block that controls the output current of the inverter so as to be synchronized with the phase of the system voltage at the time of grid connection, a voltage control block that supplies AC power of a predetermined voltage to the independent system at the time of disconnection, Functional blocks such as an isolated operation detection block for detecting whether or not the system is in an isolated operation state during grid connection are provided. The voltage control block functions as the self-sustained operation control device of the present invention.

  FIG. 2 shows a connection relationship between the system power supply 100 and the solar power generation device 1. Six-phase AC power of 6,600V is transmitted by the high-voltage distribution line composed of the three overhead lines W1, W2, W3, and the high-voltage distribution line is connected to the pole transformer 101 installed in the distribution column near the customer. Power is input from two overhead lines W1 and W3 for one phase.

  The voltage of 6,600V is stepped down to a single-phase voltage of 200V by the pole transformer 101, and an intermediate tap of 200V is taken out as a neutral line, 100V between the single line and the neutral line, and 200V between the lines. Is obtained. The neutral wire is connected to the neutral wire grounding pole near the distribution pole and grounded.

  The output of the pole transformer 101 is output to the low-voltage distribution lines L1, L2, and L3 installed on the distribution pole, and is configured on the distribution board 102 in the customer premises via the low-voltage lead-in lines N1, N2, and N3. The main circuit 104 is connected to the main circuit leakage breaker 103 or the like. A watt-hour meter for power purchase Wh1 and a watt-hour meter for power sale Wh2 are connected to the low-voltage lead-in line.

  A power supply line 105 is connected to the main circuit 104 via a breaker CB, and power is supplied from each power supply line 105 to the local load Load1. The output terminal of the power conditioner PC of the photovoltaic power generator 1 is configured to be connectable to the main circuit 104 via the system relay Ry1, and is connected to the power supply line 106 of the independent system via the independent relay Ry2 and the breaker CB. The self-supporting load Load2 is configured to be able to supply power. In the present embodiment, an AC 100V two-phase power conditioner PC will be described as an example, but the present invention is also applicable to a single-phase three-phase power conditioner PC.

  The current control block of the inverter control unit 5b controls the output current of the inverter so as to synchronize with the phase of the system voltage by closing the system relay Ry1 when the system is connected, and the isolated operation state is detected by the isolated operation detection block. Then, the system relay Ry1 is opened and disconnected from the system.

  In the independent operation control device functioning as a voltage control block of the inverter control unit 5b, when the isolated operation state is detected by the isolated operation detection block and the system relay Ry1 is opened, the independent relay Ry2 is closed and the independent system is predetermined. Supply voltage AC power.

  When power is supplied from the power conditioner 2 to the load Load 2 connected to the self-supporting system, if the output voltage deviates from the range of 101 ± 6 V due to the fluctuation of the load current, the load Load 2 cannot be stably operated. .

  Therefore, the self-sustained operation control device controls the inverter 3 so that a stable output voltage can be obtained regardless of fluctuations in the load current. This will be described in detail below.

FIG. 3 shows an equivalent circuit of the independent operation control device 50 and the inverter 3 and the LC filter 4. In FIG. 3, reference sign V _dc is a DC link voltage, C _dc is an electrolytic capacitor for DC link voltage, S _{1 to} S ₄ are switching elements of the inverter 3, e _inv is an output voltage of the inverter 3, and i _inv is an inverter 3 output current, _{L f} and _{C f} are LC filters, _{R f} is the internal resistance, _{R c} is the internal _{resistance, e sd} output voltage of the LC filter 4 during the autonomous operation of the AC side of the capacitor _{C f} of the inductor _{L f,} i _c is a current flowing through the capacitor C _f on the AC side, i _Load is a load current, R _Load is an AC load, and e _Load is a load voltage. A film capacitor is preferably used as the capacitor, but is not limited to a film capacitor.

[Equation 1] is derived based on Kirchhoff's voltage law, and [Equation 2] is derived based on Kirchhoff's current law. Here, _{u d} is the PWM duty of the single-phase inverter output.

[Expression 3] is established when the current is expressed as a command value by [Expression 2].

Further, the load current i _Load of [ _Equation 2] is obtained from [ _Equation 4]. Here, _ic is a current flowing in the capacitor C _f constituting the LC filter 4. Further, _ic can be estimated from the capacitor C _f , the internal resistance R _c, and the output voltage _{esd of the} independent operation, as shown in [Equation 5].

Also, [Expression 1] is expressed as a command value to be [Expression 6].

That is, even if the current sensor for detecting the load current i _Load is not provided, if the output current i _inv of the inverter 3 and the output voltage _esd of the LC filter 4 are detected, those are calculated based on [ _Equation 5]. The current flowing through the capacitor C _f can be estimated from the value, and the load current i _Load is obtained based on the estimated value.

The autonomous operation control device 50 is configured to control the output voltage of the inverter 3 during the autonomous operation based on the estimated value of the load current i _Load described above.

FIG. 4 shows a flow of a voltage control algorithm executed by the autonomous operation control device 50. Autonomous operation control device 50 is provided with a load current estimating unit 51 for estimating a load current _{i Load} supplied to autonomous systems on the basis of the output voltage _{e sd} output current _{i inv} and LC filter 4 of the inverter 3, the output It is configured to feedback control so that the target voltage ^e _{* sd} from the inverter 3 is output on the basis of the voltage _{e sd} to the load current _{i load.}

The self-sustained operation control device 50 includes an AC output voltage control unit 53 that sets a target current i ^* _inv of the inverter 3 by performing feedback control so as to maintain the output voltage _esd at a predetermined target voltage e ^* _sd , and target current ⁱ _{* inv} and the output current _{i inv} and the load current _{i load} on the basis of the AC output current by feedback control so that the target voltage ^e _{* sd} from the inverter 3 is output to set the duty ^u _{* d} of the inverter A control unit 54 is provided.

The duty u ^* _d set by the AC output current control unit 54 is input to the PWM control unit 55, the switching elements S _{1 to} S _{4 of} the inverter 3 are PWM controlled, and harmonic noise is removed via the LC filter 4. AC voltage is output.

Here, as described above, the load current estimation units 51 and 52 estimate the branch current _ic flowing through the capacitor C _f of the LC filter 4 based on the output current i _inv and the output voltage _esd , and the output current i _The load current i _Load is calculated by subtracting the branch current _ic from _inv .

PID control can be suitably used as the feedback control, and the AC output voltage control unit 53 uses the target current i as a linear function that multiplies the difference (deviation) between the output voltage e _sd and the target voltage e ^* _sd by the proportional gain K _ip. ^* _Inv can be set.

Further, the AC output current control unit 54 can set the duty u ^* _d as a linear function by multiplying the difference (deviation) between the output current i _inv and the target current i ^* _inv by the proportional gain K _ip, which is estimated at this time It is possible to improve control responsiveness by _treating the load current i _Load as a disturbance and setting the proportional gain K _ip variably according to the magnitude. In any of the above cases, the PID control can be configured by combining not only proportional control but also differential control and integral control.

  By the above-mentioned self-sustained operation control device 50, the inverter 3 that converts DC generated power into AC power and the LC filter 4 that removes harmonic components from the output of the inverter 3 are provided. A self-sustained operation control method for a distributed power source configured to be able to supply power is executed.

The isolated operation control method estimates the load current _{i Load} supplied to autonomous systems on the basis of the output voltage _{e sd} output current _{i inv} and LC filter 4 of the inverter 3, the output voltage _{e sd} and load current _{i Load} Based on this, feedback control is performed so that the target voltage e ^* _sd is output from the inverter.

Then, a voltage control step for feedback-controlling the target current i ^* _inv of the inverter 3 so as to maintain the output voltage e _sd at the predetermined target voltage e ^* _sd , and the independent system based on the output current i _inv and the output voltage _esd A load current estimation step for estimating a load current i _Load supplied to the inverter, and an inverter so that the target voltage e ^* _sd is output from the inverter 3 based on the target current i ^* _inv , the output current i _inv, and the load current i _Load And a current control step for feedback control of the duty ratio u ^* _d of 3.

The load current estimation step estimates the current _ic flowing through the capacitor of the LC filter 4 based on the output current i _inv of the inverter 3 and the output voltage _esd of the LC filter 4, and estimates from the output current i _{inv of the} inverter 3. In this step, the load current i _Load is calculated by subtracting the current _ic .

  In other words, according to the present invention, it is not necessary to incorporate a separate current sensor for measuring the load current and a separate circuit for suppressing the inrush current, so that a simple configuration can be realized and a complicated control algorithm can be realized. It is no longer necessary to incorporate etc.

  Also, by reflecting the estimated load current as a disturbance in the control, stabilization of the output voltage at the time of sudden load change can be improved, and fast response characteristics can be obtained by feedback of the estimated load current .

  FIGS. 6A and 6B show the results of an experiment in which the above-mentioned self-sustained operation control method is not employed and the output voltage control characteristics when the method is employed. FIG. 5 shows circuit parameter setting values during the experiment.

  FIG. 6A shows the experimental results when the estimated load current is not used, and FIG. 6B shows the experimental results when the estimated load current is used. When the estimated load current is not used for the control, about 280 ms. When the estimated load current is used, the steady state is about 20 ms. It became clear that it was in a steady state. In other words, it has become clear that stable voltage control is possible by incorporating the estimated load current into the control.

FIG. 6C shows a transient response characteristic when the above-mentioned self-sustained operation control method is adopted, that is, a load voltage characteristic when the cleaner with an output of 600 W is driven simultaneously with the self-sustained relay being closed. As is apparent from FIG. 6C, it was confirmed that the load voltage e _Load can be stably controlled even when the load current flows rapidly.

  In the above-described embodiment, the self-sustained operation control device and method in the case where power is supplied to the self-supporting load Load2 connected to the power supply line 106 of the self-supporting system via the self-supporting relay Ry2 has been described. However, as illustrated in FIG. That is, after the main circuit 104 formed in the low voltage lead-in lines N1, N2, and N3 and the distribution board 102 in the premises is interrupted by the main earth leakage circuit breaker 103 and the like, the system relay Ry1 and the feeder line 105 are used. Even when power is supplied to the local load Load1, it is also possible to apply power to the local load Load1 by applying the self-sustained operation control apparatus and method according to the present invention.

  The embodiment described above is merely an example of a self-sustained operation control device, a power conditioner, and a self-sustained operation control method for a distributed power source according to the present invention, and the technical scope of the present invention is limited by the description. Needless to say, the specific control algorithm can be changed and designed as appropriate as long as the operational effects of the present invention are achieved.

1: Distributed power supply 2: DC / DC converter 3: Inverter 4: LC filter 50: Stand-alone operation control devices 51, 52: Load current estimation unit 53: AC output voltage control unit 54: AC output current control unit 100: System power supply PC: Power conditioner SP: Solar cell panels S1, S2, S3, S4: Switch elements provided in the inverter bridge

Claims (7)

An inverter for converting DC generated power into AC power and an LC filter for removing harmonic components from the output of the inverter, and a distributed power source configured to be able to supply power to a stand-alone system when the system power source drops below a predetermined voltage a self-sustaining operation control device comprises a load current estimating unit for estimating a load current i _load supplied to the self-supporting system on the basis of the output voltage e _sd of the LC filter and the output current i _inv of the inverter, the output autonomous operation control device for a distributed power sources for feedback control so that the target voltage e ^* _sd from the inverter on the basis of the voltage e _sd to the load current i _load is output. A voltage control unit that feedback-controls the target current i ^* _inv of the inverter so as to maintain the output voltage e _sd at a predetermined target voltage e ^* _sd ; the target current i ^* _inv ; the output current i _inv; and the load autonomous distributed power source of the target voltage e ^* _sd is the inverter according to claim 1 wherein a current control unit that feedback controls the duty ratio u ^* _d to be outputted from said inverter on the basis of the current i _Load Operation control device. The load current estimating unit estimates a branch current _ic flowing through a capacitor of the LC filter based on the output current i _inv and the output voltage _esd , and subtracts the branch current _ic from the output current i _inv. The self-sustained operation control device for a distributed power supply according to claim 1 or 2, wherein the load current _iLoad is calculated by the calculation.   An inverter for converting DC generated power into AC power and an LC filter for removing harmonic components from the output of the inverter, and the independent operation control device for the distributed power source according to any one of claims 1 to 3, A power conditioner configured to control the output voltage. An inverter for converting DC generated power into AC power and an LC filter for removing harmonic components from the output of the inverter, and a distributed power source configured to be able to supply power to a stand-alone system when the system power source drops below a predetermined voltage a self-sustaining operation control method, the output current i _inv of the inverter LC based on the output voltage e _sd filter to estimate the load current i _load supplied to the self system, the load and the output voltage e _sd A self-sustained operation control method for a distributed power source, which performs feedback control so that a target voltage e ^* _sd is output from the inverter based on a current i _Load . A voltage control step of feedback-controlling the target current i ^* _inv of the inverter so as to maintain the output voltage e _sd at a predetermined target voltage e ^* _sd ; and based on the output current i _inv and the output voltage _esd a load current estimating step of estimating the load current _{i load} supplied to autonomous system, the target voltage ^e _{* sd} from the inverter on the basis of said target current ⁱ _{* inv} and the output current _{i inv} to the load current _{i load} is 6. The distributed power supply self-sustained operation control method according to claim 5, further comprising a current control step of feedback-controlling the duty ratio u ^* _d of the inverter so as to be output. The load current _{i Load} estimates branch current _{i c} flowing to the capacitor of the LC filter based and the output current _{i inv} the output voltage _{e sd,} subtracting the branch current _{i c} from the output current _{i inv} The self-sustained operation control method for a distributed power source according to claim 5 or 6, which is estimated as described above.