JP5790313B2 - Electric power leveling device - Google Patents

Description

  The present invention relates to a full charge control of an energy storage element applied to a power leveling device that compensates for power fluctuations at a grid connection point.

  In recent years, the introduction of distributed power sources using natural energy, such as solar power generation devices and wind power generation devices, has progressed. These distributed power sources are connected to a commercial power system in order to provide stable power supply. However, the amount of power generated by natural energy is generally not stable. If the amount of power generation is not stable, power fluctuations on the grid side will increase, and there is also a concern that a large-scale power outage may occur due to grid instability.

  In order to solve such problems, a power leveling device using an energy storage element such as a battery and a power converter using a switching element made of a semiconductor or the like is introduced in combination with a distributed power source, The power supply is stabilized. Conventionally, not only active power but also reactive power has been controlled, which contributes to improvement of transient stability of the power system.

  FIG. 4 is a block diagram showing an example of a power leveling device, but only a general configuration part (a part of a known technique) is shown in the figure, and a detailed description thereof is omitted (the general load 106, current shown in the figure). The detector 110, the current detector 111, and the voltage detector 109b are only shown in the figure and description thereof is omitted). Usually, in the configuration as shown in FIG. 4, the surplus power is regenerated to the commercial power system 101 side while supplying the power generated by the distributed power source 108 to the important load 115 of the consumer. However, when the fluctuation of the power flow at the grid connection point 104 is large, there is a risk of destabilizing the commercial power grid 101 side as described above, so that the power flow at the grid connection point 104 is as much as possible. Need to be leveled.

  Accordingly, the voltage of the connection line of the distributed power source 108, the power converter 112 and the important load 115 and the current flowing into the load (important load 115) side and the power converter 112 side are detected, and the load (important) A grid interconnection point is obtained by obtaining active power and reactive power on the load 115) side and the power converter 112 side and controlling the power converter 112 according to the power command values (active power command Pref and reactive power command Qref). 104 is a system for leveling power.

When a power failure occurs on the commercial power system 101 side, the power failure detection unit 103 detects the power failure. A connection point CB (Circuit Breaker) 102 disconnects the commercial power system 101 and a control device 114 that controls the power converter 112 receives a power failure detection signal. Until the emergency generator 105 starts operation, the high-speed switch (AC switch) 107 is disconnected, the power converter 112 is operated as a UPS (Uninterruptible Power Supply), and power is supplied to the important load 115. Supply.
Thereafter, when the emergency generator 105 starts operating and can supply power, the power leveling device 150 shown in FIG. 4 replaces the operation of assisting the power fluctuation of the emergency generator 105.

FIG. 5 is a conceptual diagram showing a conventional general state transition in the power leveling apparatus 150 having the configuration shown in FIG. 4, and is similar to a state (status) that can be generally performed in the configuration shown in FIG. The direction in which transition is possible is indicated by an arrow line (including a loop).
In addition, although the arrow line indicates the transition operation A and the number of the event (event) E that triggers the transition operation, this figure is a conceptual diagram for explaining each state. The detailed description of is omitted.

About each state shown in FIG. 5, it is as follows in general.
Status S00 indicates a complete stop state. Immediately after this configuration is activated.
Status S02 indicates a stop standby state. Waiting for various signals to be connected, such as immediately after the connection point CB102 is turned on.
Status S14 indicates a soft start state. The operating state of the power converter 112 or the like is shifted to a predetermined steady state in the next status over a predetermined time (capacitor charging or the like).

Status S08 indicates a commercial interconnection control state. The power converter 112 is operated by current control in conjunction with the commercial power system 101.
Status S18 indicates a commercial power failure / interconnection inverter control state. When the commercial power system 101 is blacked out and the emergency generator 105 is in operation, the power converter 112 is operated with current control in conjunction with the emergency generator 105.
Status S10 indicates a commercial power failure / CVCF control state. When the commercial power system 101 fails and the emergency generator 105 cannot supply power (during the start-up operation immediately after the power failure or when the fuel is depleted and stopped), the power converter 112 stores the energy of the energy storage element 113. Is used to control the voltage and frequency so that they are controlled independently.

JP 2008-72774 A JP 2011-10412 A

In such a prior art power leveling device 150, when no power failure occurs, the control device 114 is in the state of commercial interconnection control S08 shown in FIG. 5, and the power converter 112 controls the energy storage element 113. Controls and monitors the state of charge.
The charge / discharge control of the energy storage element 113 is performed by an active power command Pref from a host controller (external device) (not shown). When the energy storage element 113 is in a fully charged state, the host controller controls the active power command Pref to 0 [kW] and controls to be in a charge / discharge zero state.

  However, even if the active power command Pref is set to 0 [kW], charging / discharging of the energy storage element 113 is not directly controlled, so that charging / discharging occurs slightly. When this state was confirmed with an actual machine, there was often a slight discharge state, and there was a problem that the accumulated energy was released.

  The purpose of the present invention is to automatically determine the full charge control mode of the energy storage element from the active power command from the host controller using the power leveling device, and to directly charge / discharge current so that the charge / discharge of the energy storage element becomes zero. It is to provide a technology that can be controlled.

The power leveling apparatus according to the present invention includes a switch for connecting a commercial power system, an important load and a distributed power source, and an AC / DC connected to an AC side of a connection line between the switch, the important load and the distributed power source. A converter, an energy storage element connected to a DC side of the AC / DC converter, a voltage detection unit for detecting a voltage of a connection line between the switch, the important load and the distributed power source, and the important load. A first current detection unit for detecting a flowing current, a second current detection unit for detecting a current flowing on the AC side of the AC / DC converter, a third current detection unit for detecting a current flowing in the energy storage element, the voltage detecting section, and the detected value of the first current detector and the second current detector or, et al., the AC-DC converter on the basis of the power command and the reactive power command from the host controller A control unit for outputting a command to control to, and a charge and discharge control unit for outputting a command for controlling the AC-DC converter based on a detected value from the third current detector, said AC-DC converter When the absolute value of the active power command from the host controller is greater than or equal to the reference value near zero, control is performed with the command from the control unit, and when the absolute value of the active power command from the host controller is less than the reference value near zero The control is performed by switching to a command from the charge / discharge control unit .
In the power leveling device of the present invention , the charge / discharge control unit includes a low-pass filter block that removes a high-frequency component from a detection value from the third current detection unit, and a detection from the third current detection unit. A proportional-integral compensation block that performs proportional-integral compensation so that the difference between the value and the battery current reference value 0 [A] becomes zero, and a value obtained by limiting the output from the proportional-integral-compensation block You may make it consist of the limiter used as the command to control .

  According to the present invention, in a power leveling device capable of regenerating power to the commercial power system side, even when the energy storage element is in a fully charged state, the charge / discharge current is controlled to zero, so that wasteful energy release is achieved. Can provide technology that does not.

It is a block diagram which shows the structure of the power leveling apparatus based on embodiment of this invention. It is a figure which shows the state transition of the power leveling apparatus based on embodiment of this invention. It is a figure explaining each process of battery current zero control based on embodiment of this invention. It is a block diagram which shows the structural example of the power leveling apparatus based on a prior art. It is a figure which shows the state transition of the power leveling apparatus based on a prior art.

Hereinafter, a power leveling apparatus according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a power leveling device 50 according to the present embodiment.
The commercial power system 1 is configured to supply power to the important load 15 via the power leveling device 50 of the present embodiment. The grid connection point 4 is connected to the commercial power grid 1 via a grid point CB (breaker) 2 that is controlled to be cut off during a power failure or the like. The power failure detection unit 3 detects a power failure in the commercial power system 1 and sends a power failure detection signal Sd.

An emergency generator 5 and a general load 6 are connected to the grid connection point 4 and also connected to an important load connection point 9 a via a high-speed switch (AC switch for connecting and disconnecting power) 7. The important load connection point 9a is a voltage detector 9b.
A distributed power source 8 such as a photovoltaic power generation facility, a wind power generation facility, a fuel cell, or a regular private power generation facility is connected to the important load connection point 9a, and a power converter 12 is connected via a current detector 10. Also, an important load 15 is connected via the current detector 11.

  In addition to the detection value by the voltage detector 9b, the detection value by the current detector 10 and the detection value by the current detector 11, the control device 14 receives a detection value (battery current value Dib) by a current detector 30 described later. In addition, the control device 14 receives the active power command Pref and the reactive power command Qref from the host controller 18 (external device) and controls the power converter 12.

  The control device 14 consists of several blocks. The control unit 20 performs power conversion based on the detection value by the voltage detector 9b, the detection value by the current detector 10, the detection value by the current detector 11, and the active power command Pref and the reactive power command Qref from the host controller 18. The control unit 20 outputs a first Ip command (not shown, for convenience, Ip20) for controlling the device 12.

The charge / discharge control unit 26 outputs a second Ip command (not shown, but is referred to as Ip26 for convenience) for controlling the power converter 12 based on a value detected by the current detector 30 (battery current value Dib).
Both the first Ip command (Ip20) and the second Ip command (Ip26) are sent to the switching unit 24. When the active power command Pref is zero (when the absolute value of the active power command Pref is less than an arbitrary reference value close to 0 [kW]), the switching unit 24 instructs the second Ip command ( Ip26) is selected, and when the active power command Pref is not less than a predetermined value that is not zero (when the absolute value of the active power command Pref is not less than an arbitrary reference value close to 0 [kW]), the instruction of the determination unit 22 To select the first Ip command (Ip20), and send it to the power converter 12 as the Ip command.

The power converter 12 described above is an AC / DC converter that can convert AC power and DC power to each other, and charges the energy storage element 13 with a part of the power at the important load connection point 9a, and It plays the role of converting the energy stored in the energy storage element 13 into electric power of a predetermined frequency and voltage by pulse width modulation and supplying it to the important load connection point 9a. The current detector 30 detects the battery current value Dib between the power converter 12 and the energy storage element 13.
The energy storage element 13 is a secondary battery such as a lead storage battery, for example.

FIG. 2 is a diagram illustrating an example of state transition of the power leveling device 50 according to the present embodiment. In FIG. 2, states (status) that can be taken in the present embodiment and directions that can similarly be changed are indicated by arrow lines (including loops).
Since these states are the same as those shown in FIG. 5 except for the inside of the broken line, which is a feature of the present invention, the same reference numerals are given, and detailed explanations are omitted.
A detailed description of A representing the transition operation and the number of the event E that triggers the transition operation will be omitted except for portions necessary for the description of the present embodiment.

As described above, the portion within the broken line in FIG. 2 is a feature of the present invention, and is a state transition related to the full charge control of the energy storage element 13.
S09 is full charge control for controlling charging / discharging of the energy storage element 13 via the power converter 12. The full charge control S09 is a commercial interconnection control S08 that performs power leveling control triggered by an event E16 in which the absolute value of the active power command Pref received from the host controller 18 is less than an arbitrary reference value near 0 [kW]. Transition from only. This arbitrary reference value is an adjustment factor in the installation environment of the power leveling device 50 of the present embodiment, and can be changed.

  The operation for changing the state from the commercial interconnection control S08 to the full charge control S09 is A16 with respect to the event E16. In the operation A16, active power control, which will be described later, is continued with the battery current zero control S09a, and the reactive power control is stopped.

  On the other hand, there are three transitions from the full charge control S09 to the other control, and the first is the operation A17 for the event E17. The event E17 occurs when the absolute value of the active power command Pref received from the host controller 18 is equal to or larger than an arbitrary reference value near 0 [kW]. Operation A17 at this time makes a transition to commercial interconnection control S08, active power control continues from zero battery current control by control according to active power command Pref from host controller 18, and reactive power control from host controller 18 Control is started by the reactive power command Qref.

  The second is the operation A05 for the event E05. The operation A05 is a stop operation during the full charge control S09. The active power control and the reactive power control are ended, and the control system variables and signal settings are set at the stop time. Then, the state transition is made to the stop standby S02.

  The third is the operation A04 for the event E04. Operation A04 is a power failure backup operation during the full charge control S09. The active power control and the reactive power control are terminated, and the control system variables and signal settings are set at the time of the power failure. Then, the commercial power failure / CVCF (Constant Voltage The state transitions to the control frequency (S10), and the backup operation during a power failure is performed.

Next, the battery current zero control S09a during the full charge control S09 of the energy storage element 13 will be described based on the block diagram of FIG. The battery current zero control S09a includes the following processes.
St1: LPF (low pass filter) block St2: -1 times gain (polarity inversion)
St3: PI (proportional integral compensation) block St4: Limiter (limiter)

In St1, the high-frequency component is removed by the LPF from the battery current value Dib detected by the current detector 30, and in St2 that follows, this value is multiplied by -1. This is for obtaining a difference with respect to the battery current command value 0 [A] (fixed). Here, the polarity is reversed, and then the battery current reference value 0 [A] is added.
The adder 40 provided between St2 and St3 can be omitted because it only adds 0.
Thereafter, PI compensation is performed at St3, and a value obtained by limiting the output at St4 is defined as a first Ip command (Ip26).

Here, when the charge / discharge control unit 26 has the configuration shown in the block diagram of FIG. 3, gate signal generation that generates a control signal for driving the power converter 12 based on the Ip command (Ip26) output from St2. It is necessary to provide a circuit (coordinate conversion circuit, pulse width control signal generation circuit, etc.).
The gate signal generation circuit is provided in the charge / discharge control unit 26, but the control unit 20 is also provided with the same type of gate signal generation circuit. In this case, the switching unit 24 can be configured to switch the output signals of the gate signal generation circuits of the charge / discharge control unit 26 and the control unit 20.
In addition, since the gate signal generation circuit provided in the charge / discharge control unit 26 and the gate signal generation circuit provided in the control unit 20 can have the same configuration, a common set is provided in the switching unit 24 for switching. be able to. This simplifies the configuration because only one set of gate signal generation circuits need be provided.

Thus, in the present embodiment, when the active power command Pref is zero, the difference between the battery current value Dib and the battery current reference value 0 [A] (battery current command value 0 [A]) is zero. Thus, the battery current value Dib is controlled to 0 [A].
That is, when the energy storage element is in a fully charged state, the charge / discharge current is controlled to zero, and no unnecessary energy is released.

  The present invention has been described above based on the embodiments. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to combinations of the respective components and processes, and such modifications are also within the scope of the present invention.

1 Commercial power system 2 Interconnection point CB
3 Power failure detection unit 4 Grid connection point 5 Emergency generator 6 General load 7 High-speed switch (switch)
8 Distributed power source 9a Important load connection point 9b Voltage detector (voltage detector)
10 Current detector (second current detector)
11 Current detector (first current detector)
12 Power converter (AC / DC converter)
13 Energy Storage Element 14 Control Device 15 Important Load 18 Host Controller 20 Control Unit 22 Discrimination Unit 24 Switching Unit 26 Charge / Discharge Control Unit 30 Current Detector (Third Current Detection Unit)
50, 150 Power leveling device Sd Power failure detection signal Dib Battery current value Pref Active power command Qref Reactive power command

Claims (2)

A switch for connecting the commercial power system with important loads and distributed power sources;
An AC / DC converter having an AC side connected to a connection line between the switch and the important load and the distributed power source;
An energy storage element connected to the DC side of the AC / DC converter;
A voltage detection unit for detecting a voltage of a connection line between the switch and the important load and the distributed power source;
A first current detector for detecting a current flowing through the important load;
A second current detector for detecting a current flowing on the AC side of the AC / DC converter;
A third current detector for detecting a current flowing through the energy storage element;
The voltage detection unit, a command for controlling the detection values of the first current detector and the second current detector or al, the AC-DC converter on the basis of the power command and the reactive power command from the host controller A control unit for outputting
A charge / discharge control unit that outputs a command to control the AC / DC converter based on a detection value from the third current detection unit ,
When the absolute value of the active power command from the host controller is greater than or equal to a reference value near zero, the AC / DC converter is controlled by a command from the control unit, and the absolute value of the active power command from the host controller is zero. The power leveling device is controlled by switching to a command from the charge / discharge control unit if it is less than a nearby reference value . The charge / discharge control unit includes a low-pass filter block that removes a high-frequency component from a detection value from the third current detection unit, a detection value from the third current detection unit, and a battery current reference value 0 [A]. A proportional-integral compensation block that performs proportional-integral compensation so that the difference between them is zero, and a limiter that uses a value obtained by limiting the output from the proportional-integral-compensation block as a command for controlling the AC / DC converter. The power leveling device according to claim 1, wherein:

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