JP2024031469A - Electrical power system and control method of electrical power system - Google Patents

Abstract

To provide an electrical power system having a configuration simplified by integrating a device for assisting opening of a breaker and a device for compensating a voltage of a load after opening of the breaker.SOLUTION: An electrical power system comprises: a mechanical switch 3 that is provided in an electric power line L1 for supplying electric power from an electric power system 10 to a load 20, and opens and close the electric power line L1; a switch controller 91 for controlling the mechanical switch 3; a power converter 8 that is connected to the electric power line L1 and coverts direct-current power of a capacitor 7 into alternating-current power and supplies the alternating-current power to the electric power line L1; a power converter controller 92 for controlling the power converter 8; and an abnormality detector 6 that when an abnormality of the power electric power system 10 is detected, outputs an open instruction C for the mechanical switch 3 to the switch controller 91. The power converter controller 92 performs current interruption control in response to the output of the open instruction C. In the current interruption control, the power converter 8 is subjected to feedback control in a manner that the current flowing to the mechanical switch 3 becomes zero. After the current interruption control, the power converter controller 92 performs voltage compensation control that controls the power converter 8 to compensate the voltage of the load 20.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power supply system and a method of controlling the power supply system.

In conventional power supply systems, when an abnormality occurs in the power system, the power supply from the power system to the load is cut off by opening a circuit breaker installed in the power line that supplies power from the power system to the load. Then, after the power grid has been disconnected from the load, the distributed power source connected to the load side supplies power to the load, thereby compensating the voltage of the load.

In this type of power supply system, a power supply system that further includes a commutation circuit connected in parallel with the circuit breaker is proposed, as shown in Patent Document 1, for example, to assist in opening the circuit breaker. In this power supply system, when an abnormality is detected in the power system, the circuit breaker is opened and a commutation circuit is turned on at the same time.The commutation circuit superimposes harmonic current on the fault current flowing through the circuit breaker, and It forms the zero point. As a result, a current zero point is forcibly formed, so that the circuit breaker opens in a short time and the load is disconnected from the power system. The distributed power source then supplies power to the load and compensates for the load voltage.

Japanese Patent Application Publication No. 2003-264932

Here, in the above power supply system, a commutation circuit is used when assisting the opening of the circuit breaker, while a distributed power supply is used when compensating the voltage of the load after opening the circuit breaker. That is, in this type of power supply system, the device that assists in opening the circuit breaker and the device that compensates for the voltage of the load after opening the circuit breaker are different, resulting in a complicated configuration of the power supply system.

Therefore, the present invention was made in view of the above problem, and the configuration of the power supply system is improved by using a device that assists in opening the circuit breaker and a device that compensates for the voltage of the load after opening the circuit breaker. The main challenge is to make it simple.

That is, the power supply system according to the present invention is provided on a power line for supplying power from a power system to a load, and includes a mechanical switch that opens and closes the power line, a switch control unit that controls the mechanical switch, and a switch control unit that is connected to the power line. , a power converter that converts DC power in a power storage unit into AC power and supplies power to the power line; a power converter control unit that controls the power converter; an abnormality detection unit that outputs an opening command for the mechanical switch to the switch control unit, and the power converter control unit is configured to reduce the current flowing through the mechanical switch to zero in response to the output of the opening command. Current cutoff control is performed to perform feedback control of the power converter, and after the current cutoff control, voltage compensation control is performed to control the power converter to compensate for the voltage of the load.

In such a power supply system, in the current cutoff control, the power converter controlled by the power converter control unit supplies power to the power line so that the current flowing through the mechanical switch becomes zero. Further, in voltage compensation control, a power converter controlled by a power converter control unit supplies power to the power line so as to compensate for the voltage of the load. In other words, the device that supplies power to assist in opening the mechanical switch and the device that supplies power to compensate for the voltage of the load are shared by the power converter, which simplifies the configuration of the power supply system. can do.
Further, since the power converter control unit performs feedback control on the power converter so that the current flowing through the mechanical switch is zero, a current zero point of the current flowing through the mechanical switch is forcibly formed. Therefore, the mechanical switch can be opened faster and therefore the load can be disconnected from the power system faster.

The power converter control unit further includes a switch current measurement unit that measures a current flowing through the mechanical switch and outputs the measured value to the power converter control unit, and the power converter control unit Preferably, the power converter is proportionally controlled based on a deviation between a command value that sets the current flowing through the switch to zero and the measured value.
With this power converter control unit, proportional control is performed according to the deviation between the command value and the measured value to zero the current flowing through the mechanical switch, so the current zero point of the current flowing through the mechanical switch is forced. The mechanical switch can be opened in a shorter time.

The power converter control unit calculates a voltage target value, which is a target voltage value in the power converter, so that the current flowing through the mechanical switch is zero, and sets the voltage target value within a predetermined range. It is desirable to further include a limiter section.
With this power converter control unit, the limiter unit limits the voltage target value within a predetermined range, so when power is supplied from the power converter to the power line, it is possible to prevent excessive power from being supplied to the power line. This can prevent overcurrent in the power converter.

When the opening of the mechanical switch is completed, the switch control unit outputs an opening completion signal indicating completion of opening of the mechanical switch to the power converter control unit, and the power converter control unit , switching from the current cutoff control to the voltage compensation control in response to the output of the opening completion signal.
With such a configuration, the load is completely cut off from the power system by outputting the open completion signal, and in this state, the power converter control section can switch from current cutoff control to voltage compensation control. becomes. Then, the power converter control section performs voltage compensation control, and the power converter supplies power to the load, so that the voltage of the load can be reliably compensated.

The power converter control unit may switch from the current cutoff control to the voltage compensation control after a predetermined time has elapsed since the open command was output.
With such a configuration, voltage compensation control is switched to voltage compensation control after a predetermined period of time has passed after the opening command is output, so even if a problem occurs with the opening completion signal from the switch control unit, voltage compensation control can be performed reliably. can be started. For example, even if the switch control unit fails and the opening completion signal is not output, or even if there is a delay between the opening completion signal being output and reaching the power converter control unit, the power converter control unit After a predetermined period of time has elapsed since the opening command was output, it is possible to switch from current cutoff control to voltage compensation control.

Further, as a control method for a power supply system according to the present invention, power is supplied from the power system to the load when the power system is normal, and power supply from the power system to the load is cut off when the power system is abnormal, and the power storage unit A method for controlling a power supply system that supplies power to the load from the power system, the power supply system including a mechanical switch that is provided on a power line for supplying power from the power system to the load, and that is connected to the power line. and a power converter that converts DC power in the power storage unit to AC power and supplies the power to the power line, and outputs an opening command for the mechanical switch when an abnormality in the power system is detected. , in accordance with the output of the open command, performs current cutoff control that feedback controls the power converter so that the current flowing through the mechanical switch is zero, and after the current cutoff control, compensates for the voltage of the load. The present invention is characterized in that voltage compensation control is performed to control the power converter so as to.

According to the present invention configured in this way, the configuration of the power supply system can be simplified by using a common device for assisting in opening the circuit breaker and a device for compensating the load voltage after opening the circuit breaker. .

FIG. 1 is a schematic diagram showing the configuration of a power supply system in this embodiment. It is a schematic diagram which shows the control block in the same embodiment. It is a schematic diagram which shows the conditions of the limiter part in the same embodiment. It is a timing chart explaining current interruption control and voltage compensation control in the same embodiment.

EMBODIMENT OF THE INVENTION Below, one Embodiment of the power supply system based on this invention is described with reference to drawings. Note that any of the figures shown below may be appropriately omitted or exaggerated and schematically drawn in order to make it easier to understand. Identical components will be designated by the same reference numerals and descriptions will be omitted as appropriate.

<1. Device configuration>
As shown in FIG. 1, a power supply system 100 in this embodiment is provided between a power system 10 and a load 20, and forms a three-phase circuit. This power supply system 100 supplies power from the power system 10 to the load 20 when the power system 10 is normal, and cuts off power supply from the power system 10 to the load 20 when the power system 10 is abnormal due to a short circuit accident or the like in the power system 10. , supplies power from the power storage unit 7 to the load 20. Note that although the power supply system 100 in this embodiment is a three-phase circuit, it may be a one-phase circuit, and the number of phases is not particularly limited.

Specifically, the power supply system 100 includes a mechanical switch 3 that switches the power supply from the power system 10 to the load 20 by opening/closing it, a voltage measuring section 4 that measures the voltage generated in the power system 10, and a current flowing through the mechanical switch 3. A switch current measurement unit 5 that measures the current, an abnormality detection unit 6 that detects an abnormality in the power system 10, a power converter 8 that converts DC power in the power storage unit 7 into AC power and supplies power to the power line L1, and a mechanical switch. 3 and a control device 9 that controls the power converter 8.

The mechanical switch 3 is provided on the power line L1 for feeding power from the power system 10 to the load 20, and switches the opening and closing of the power line L1 by mechanical operation. The mechanical switch 3 switches the supply and cutoff of power supply from the power system 10 to the load 20 by switching connection and disconnection between terminals. The mechanical switch 3 is preferably provided closer to the load 20 than the power system 10 in order to more quickly cut off the power supply from the power system 10 to the load 20 when an abnormality occurs in the power system 10. It is not limited to this.

The voltage measurement unit 4 measures the voltage generated in the power system 10 and outputs the measured voltage to the abnormality detection unit 6. Specifically, as shown in FIG. 1, the voltage measurement unit 4 is connected to the power line L1 via a grid transformer 41, and is equipped with a mechanical switch so that the voltage of the power grid 10 can be measured more quickly. 3, the voltage on the power grid 10 side is measured.

The switch current measuring section 5 measures the current flowing through the mechanical switch 3 and outputs the measured value I to the control device 9. Specifically, the switch current measurement unit 5 is provided on the power line L1, as shown in FIG. 1, and measures the current on the power system 10 side rather than the mechanical switch 3. More specifically, as shown in FIG. 1, the switch current measurement unit 5 is provided between the connection point between the power converter 8 and the power line L1, and is connected in series to the mechanical switch 3 and connected to the power converter 8. connected in parallel.

The abnormality detection unit 6 outputs an opening command C to open the mechanical switch 3 when an abnormality in the power system 10 is detected. In this embodiment, the abnormality detection unit 6 detects an abnormality in the power system 10 based on the voltage measured by the voltage measurement unit 4. Specifically, the abnormality detection unit 6 determines that there is an abnormality in the power system 10 when the system voltage becomes less than the set value for a plurality of cycles. Note that the set value in this embodiment is a voltage value for detecting an instantaneous voltage drop or a power outage.

The power storage unit 7 is, for example, a power storage device (power storage device) such as a secondary battery (storage battery). This power storage unit 7 stores DC power, and when an abnormality in the power system 10 is detected, the DC power stored in the power storage unit 7 is supplied to the power converter 8.

Power converter 8 is connected to power line L1 via injection transformer T, and converts the DC power of power storage unit 7 into AC power and supplies the AC power to power line L1. Specifically, the power converter 8 is connected in parallel to the mechanical switch 3 on the power line L1, as shown in FIG.

The specific configuration of the power converter 8 includes an inverter 81 that converts DC power from the power storage unit 7 into AC power, and a grid interconnection reactor that is connected in series to the output side of the inverter 81 and stabilizes the AC current. 82, and a capacitor 83 that is connected to the interconnection reactor 82 and stabilizes the voltage. Note that interconnection reactor 82 and capacitor 83 may be connected to the input side of inverter 81 in order to rectify the DC power of power storage unit 7 .

The control device 9 controls the mechanical switch 3 and the power converter 8 when an abnormality occurs in the power system 10. The control device 9 includes a switch control section 91 that controls the mechanical switch 3 and a power converter control section 92 that controls the power converter 8.

The switch control unit 91 controls turning the mechanical switch 3 on and off. In this embodiment, the switch control unit 91 receives the opening command C output by the abnormality detection unit 6 and performs control to open the mechanical switch 3. When the opening of the mechanical switch 3 is completed, the switch control section 91 outputs an opening completion signal S indicating completion of opening of the mechanical switch 3 to the power converter control section 92.

In response to the open command C output by the abnormality detection unit 6, the power converter control unit 92 performs current cutoff control to feedback control the power converter 8 so that the current flowing through the mechanical switch 3 is zero. After the current cutoff control, voltage compensation control is performed to control the power converter 8 to compensate for the voltage of the load 20. Specifically, as shown in FIG. 2, the power converter control unit 92 includes a current cutoff control unit 921 that performs current cutoff control, a limiter unit 922 that limits control by the current cutoff control unit 921 to within a predetermined range, It includes a voltage compensation control section 923 that performs voltage compensation control, and an output control section 924 that controls the power converter 8 based on the output from the current cutoff control section 921 or the voltage compensation control section 923.

The current cutoff control unit 921 performs current cutoff control that performs feedback control on the power converter 8 so that the current flowing through the mechanical switch 3 becomes zero in response to the output of the open command C. In this embodiment, as shown in FIG. 2, the current cutoff control unit 921 controls the deviation ΔI between the measurement value I output by the switch current measurement unit 5 and the command value Iref that sets the current flowing through the mechanical switch 3 to 0. Based on this, proportional control using the proportional gain Kp is performed, and a voltage target value Vout, which is the target value of the voltage in the power converter 8, is calculated. Note that in this embodiment, the proportional gain Kp satisfies equation (1).
Kp≧V ² /S (V: rated voltage, S: rated capacity of power converter 8) (1)

The limiter section 922 is included in the current cutoff control section 921 and controls the voltage target value Vout so that it falls within the range of the maximum voltage Vmax expressed by equation (2). The limiter section 922 compares the voltage target value Vout and the maximum voltage Vmax, and if the voltage target value Vout is within the range of the maximum voltage Vmax, the limiter section 922 outputs the voltage target value Vout to the output control section 924. On the other hand, if the voltage target value Vout exceeds the range of the maximum voltage Vmax, the limiter section 922 outputs the maximum voltage Vmax to the output control section 924. Note that the impedance Z is constituted by a interconnection reactor 82, a capacitor 83, and an injection transformer T, as shown in FIG.
Vmax=Imax×Z (Imax: maximum current, Z: impedance) (2)

The voltage compensation control unit 923 controls the power converter 8 to compensate for the voltage of the load 20 that has decreased due to the current cutoff control. Specifically, as shown in FIG. 2, the voltage compensation control unit 923 sets a voltage compensation value for compensating the voltage of the load 20 based on the deviation between the voltage V measured by the voltage measurement unit 4 and the voltage command value Vref. is calculated, and the power converter 8 is feedback-controlled.

The output control section 924 receives the output from the current cutoff control section 921 or the voltage compensation control section 923 and controls the power converter 8 so that a predetermined voltage is generated. Specifically, the output control unit 924 controls the power converter 8 based on the voltage target value Vout or the maximum voltage Vmax calculated by the current cutoff control unit 921. Further, the output control section 924 controls the power converter 8 based on the voltage compensation value calculated by the voltage compensation control section 923.

Further, the output control section 924 receives the opening completion signal S and outputs a switching signal for switching from current interruption control to voltage compensation control to the current interruption control section 921 and voltage compensation control section 923. On the other hand, if a predetermined time elapses from the output of the opening command C before the output control section 924 receives the opening completion signal S, the output control section 924 transfers the switching signal to the current cutoff control section 921 and the voltage compensation control. 923. Note that the predetermined time here refers to, for example, 2 ms after the release command C is output, but is not limited to this value.

<2. Power system control operation>
Next, the control operation of the power supply system 100 will be explained.

(1) When the power system 10 is normal The voltage measurement section 4 constantly measures the voltage of the power system 10 and inputs the measured voltage to the abnormality detection section 6. The abnormality detection section 6 compares the voltage measured by the voltage measurement section 4 with a predetermined set value.

When the power system 10 is normal, the voltage measured by the voltage measurement unit 4 is equal to or higher than the set value, and the mechanical switch 3 is in a closed state. As a result, AC power is supplied from the power system 10 to the load 20.

(2) When the power system 10 is abnormal When the power system 10 is abnormal, the voltage measured by the voltage measurement unit 4 becomes less than the set value. At this time, the abnormality detection unit 6 outputs an opening command C to the control device 9, which instructs the mechanical switch 3 to open.

In response to the open command C, the power converter control unit 92 performs current cutoff control on the power converter 8, and the power converter 8 converts the DC power from the power storage unit 7 into AC power and connects the power line to the power converter 8. Supplies power to L1. Since this AC power is supplied so that the current flowing through the mechanical switch 3 is zero, the current flowing through the mechanical switch 3 is forced to form a current zero point. When the current zero point is formed, the switch control unit 91 opens the mechanical switch 3 via a drive circuit (not shown).

When the mechanical switch 3 is opened and the switch control section 91 outputs the opening completion signal S, the output control section 924 outputs a switching signal for switching from current interruption control to voltage compensation control to the current interruption control section 921 and voltage compensation control. It is output to section 923. Note that if a predetermined time has elapsed from the output of the open command C before the open completion signal S is output, the output control unit 924 forcibly outputs the switching signal.

Upon receiving the switching signal from the output control section 924, the current interruption control section 921 ends the current interruption control. On the other hand, the voltage compensation control unit 923 controls the power converter 8 to compensate for the voltage of the load 20 that has decreased due to the current cutoff control. As a result, as shown in FIG. 4, the voltage of the load 20 decreases at the initial stage when switching from current cutoff control to voltage compensation control, but due to voltage compensation control, the voltage of the load 20 decreases from the power converter 8 to the load. Power is supplied to 20. Then, after the voltage of the load 20 is compensated, the voltage of the power system 10 is restored.

<Effects of this embodiment>
According to this embodiment, the power converter 8 supplies power to the mechanical switch 3 and the load 20 under the control of the power converter control unit 92, so that a device for assisting opening of the mechanical switch 3 and a mechanical The device for compensating the voltage of the load 20 after opening of the switch 3 can be shared by the power converter 8.

In addition, the power converter control unit 92 performs feedback control of the power converter 8 so that the current flowing through the mechanical switch 3 becomes 0 during current cutoff control, so that the current flowing through the mechanical switch 3 is forced to It is possible to form a current zero point essentially. As a result, the mechanical switch 3 can be opened more quickly, so that the power supply from the power system 10 to the load 20 can be cut off more quickly.

<Other embodiments>
Note that the present invention is not limited to the above embodiments.

Although the abnormality detection unit 6 in this embodiment detects an abnormality in the power system 10 based on a change in the system voltage, the detection of an abnormality is not limited to this. For example, the abnormality detection unit 6 may detect an abnormality in the power system 10 based on a change in current or frequency in the power system 10. Accordingly, the set value of the abnormality detection unit 6 is not limited to the voltage value of the power system 10, but may be a current value or frequency in the power system 10.

The output control unit 924 in this embodiment forcibly switches from current cutoff control to voltage compensation control when a predetermined time has elapsed since the opening command C was output before the opening completion signal S was output. However, the time when the open command C is output does not have to be the starting point. For example, the starting point is the time when an abnormality in the power system 10 is detected, the time when the current cutoff control unit 921 starts control, or the time when the measured value I of the current flowing through the mechanical switch 3 becomes 0. The output control unit 924 may forcibly switch from current cutoff control to voltage compensation control after a predetermined time has elapsed from the time set as the starting point.

In this embodiment, power is supplied from the power system 10 to the load 20 using AC power, but power may be supplied from the power system 10 to the load 20 using DC power.

In addition, it goes without saying that the present invention is not limited to the embodiments described above, and that various modifications can be made without departing from the spirit thereof.

100...power supply system 10...power system 20...load 3...mechanical switch 4...voltage measurement section 5...switch current measurement section 6...abnormality detection section 7... Power storage unit 8...Power converter 9...Control device 91...Switch control unit 92...Power converter control unit L1...Power line C...Opening command S...Opening completion signal

Claims (6)

A mechanical switch that is provided on a power line for supplying power from a power system to a load and opens and closes the power line;
a switch control unit that controls the mechanical switch;
a power converter connected to the power line, converting DC power of the power storage unit into AC power and supplying power to the power line;
a power converter control unit that controls the power converter;
an abnormality detection unit that outputs a command to open the mechanical switch to the switch control unit when an abnormality in the power system is detected;
The power converter control unit performs current cutoff control that performs feedback control of the power converter so that the current flowing through the mechanical switch is zero in response to the output of the open command, and after the current cutoff control, , a power supply system that performs voltage compensation control to control the power converter to compensate for the voltage of the load. further comprising a switch current measurement unit that measures the current flowing through the mechanical switch and outputs the measured value to the power converter control unit,
The power supply system according to claim 1, wherein the power converter control unit proportionally controls the power converter based on a deviation between a command value that sets the current flowing through the mechanical switch to zero and the measured value. The power converter control unit calculates a voltage target value that is a target voltage value in the power converter so that the current flowing through the mechanical switch is zero,
The power supply system according to claim 2, further comprising a limiter section that limits the voltage target value within a predetermined range. The switch control unit outputs an opening completion signal indicating completion of opening of the mechanical switch to the power converter control unit when opening of the mechanical switch is completed;
The power supply system according to any one of claims 1 to 3, wherein the power converter control unit switches from the current cutoff control to the voltage compensation control upon receiving the output of the open completion signal. The power supply system according to claim 4, wherein the power converter control unit switches from the current cutoff control to the voltage compensation control after a predetermined time has elapsed after receiving the open command. A control method for a power supply system that supplies power from the power system to a load when the power system is normal, cuts off power supply from the power system to the load when the power system is abnormal, and supplies power from a power storage unit to the load. ,
The power supply system includes a mechanical switch that is provided on a power line for supplying power from the power system to the load and that opens and closes the power line;
and a power converter connected to the power line and converting DC power of the power storage unit into AC power and supplying power to the power line,
outputting a command to open the mechanical switch when an abnormality in the power system is detected;
In accordance with the output of the open command, current cutoff control is performed to feedback control the power converter so that the current flowing through the mechanical switch is zero, and after the current cutoff control, the voltage of the load is compensated. A method for controlling a power supply system, which performs voltage compensation control to control the power converter.