JP2014222992A - System stabilization device and system stabilization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system stabilization device and a system stabilization method, in which power control is appropriately performed in consideration of operation condition of an existing power generator.SOLUTION: A system stabilization device 14 of the present invention is a system stabilization device which stabilizes voltage of a bus bar 1 connected with a synchronous generator 4 and connected with a storage battery 5 via an inverter 6, and includes: a system information measurement section for measuring system information containing at least a power flow from the synchronous generator to the bus bar and a power flow from the inverter to the bus bar; a reactive power supply quantity determination section for determining the total value of values of respective reactive power quantities of the synchronous generator and the inverter requiring for stabilization as a reactive power supply quantity based on the system information; a reactive power share quantity determination section for determining a reactive power share quantity, which is a share quantity of the reactive power supply quantity, for the respective synchronous generator and inverter based on a total power loss of the synchronous generator and the inverter; and a control signal transmission section for transmitting control signal indicating the reactive power share quantity of the inverter to the inverter.

Description

  The present invention relates to a system stabilization apparatus and a system stabilization method, and particularly to a system stabilization apparatus and a system stabilization method for stabilizing an electric power system when renewable energy is introduced. .

  When a power generator derived from renewable energy (hereinafter referred to as “renewable energy equipment”) is introduced in the power grid, especially in small-scale power grids such as remote islands, in addition to output fluctuations, voltage fluctuations are large and the burden on existing generators is large. To increase. When output fluctuations and voltage fluctuations become large, it is not possible to stabilize the power system using only the existing generator.

  Therefore, when the renewable energy equipment capacity becomes larger than the scale of the power system, it is conventionally attempted to stabilize by absorbing the output fluctuation and voltage fluctuation in the power system by introducing a storage battery or the like. For example, in Patent Document 1, an active power control amount is calculated from a short period component of active power fluctuation due to a distributed power source or the like, frequency fluctuation is suppressed, and reactive power is calculated based on the long period component of active power and reactive power fluctuation amount. Control amount is calculated to suppress voltage fluctuation.

Japanese Patent No. 3108054

  However, in the conventional system stabilization method, the reactive power control amount is calculated regardless of the operation state of the existing generator, and therefore, the power loss, the reactive power controllable range of the existing generator, and the like are not considered. Therefore, useless power may be consumed.

  In view of the above-described problems, an object of the present invention is to provide a system stabilizing device and a system stabilizing method that appropriately perform power control in consideration of the operating state of an existing generator.

  The system stabilization device of the present invention is a system stabilization device that stabilizes the voltage of a system to which a synchronous generator is connected and a storage battery is connected via an inverter, and a power flow that flows from the synchronous generator to the system. A system information measuring unit that measures system information including at least current flowing from the inverter to the system, and based on the system information, the total value of the reactive power amount of the synchronous generator and the inverter necessary for stabilization is used as the reactive power supply amount. Reactive power sharing amount that determines the reactive power sharing amount for each reactive power generator and inverter based on the total power loss of the reactive power supply determining unit and the synchronous generator and inverter. A determination unit; and a control signal sending unit that sends a control signal indicating the reactive power share of the inverter to the inverter.

  The system stabilization device of the present invention is a system stabilization device that stabilizes the voltage of a system to which a synchronous generator is connected and a storage battery is connected via an inverter, and a power flow that flows from the synchronous generator to the system. A system information measuring unit that measures system information including at least current flowing from the inverter to the system, and based on the system information, the total value of the reactive power amount of the synchronous generator and the inverter necessary for stabilization is used as the reactive power supply amount. Reactive power sharing amount that determines the reactive power sharing amount for each reactive power generator and inverter based on the total power loss of the reactive power supply determining unit and the synchronous generator and inverter. A determination unit; and a control signal sending unit that sends a control signal indicating the reactive power share of the inverter to the inverter. Therefore, the power control is appropriately performed in consideration of the operation status of the existing generator.

It is a block diagram of the system | strain stabilization apparatus in this invention. It is a block diagram which shows the hardware constitutions of the system | strain stabilization apparatus in this invention. It is a characteristic view which shows the reactive power output possible range of a synchronous generator. It is a characteristic view which shows the reactive power output possible range of an inverter. It is a flowchart of the system | strain stabilization method in this invention. It is a figure which shows the inverter reactive power characteristic of electric power loss. It is a figure which shows the reactive power output possible range of the inverter in the modification of Embodiment 1. FIG.

<A. Embodiment 1>
<A-1. Configuration>
FIG. 1 is a configuration diagram of a power system of the first embodiment. The power system of the first embodiment includes a synchronous generator 4, a storage battery 5, a load 7, a wind power generator 8, and a system stabilizing device 14. The synchronous generator 4 is connected to the bus 1, and the storage battery 5 is also connected to the bus 1 via the inverter 6. The bus 1 is connected to the power transmission line 2 at the interconnection point 3, and a load 7 and a wind power generator 8 are connected to the tip of the power transmission line 2. A connecting line between the inverter 6 and the bus 1 is provided with a current transformer 9A which is a sensor for measuring a power flow flowing from the inverter 6 to the system. The connecting line between the synchronous generator 4 and the bus 1 is provided with a current transformer 9B that is a sensor for measuring a power flow flowing from the synchronous generator 4 to the system. The measurement results of the current transformers 9A and 9B are input to the system stabilizing device 14 through the input cable 11A.

  The voltage of the bus 1 is measured by the measuring transformer 10 and input to the system stabilizing device 14 through the input cable 11B.

  The system stabilizing device 14 acquires information by the above-described input cables 11A and 11B, and also acquires the characteristics of the generator and other information from the power supply command station by the communication path 13. Then, the voltage of the bus 1 is stabilized by controlling the reactive power of the inverter 6 based on these pieces of information.

  The system stabilizing device 14 includes a sensor input unit 141, a reactive power supply amount determination unit 142, a reactive power sharing amount determination unit 143, and a control signal output unit 144. The sensor input unit 141 acquires system information from the input cables 11A and 11B described above, and acquires the generator characteristics and system information from the power supply command center and the like through the communication path 13. Here, the system information includes the power flow value of the synchronous generator 4, the power flow value of the inverter 6, the impedance from the inverter 6 to the bus 1, the impedance from the synchronous generator 4 to the bus 1, the conversion loss rate of the inverter 6, the synchronous power generation The power generation loss rate of the machine 4 is included.

  The reactive power supply amount determination unit 142 determines the reactive power supply amount based on the information acquired by the sensor input unit 141. The reactive power supply amount is the sum of reactive power sharing amounts allocated to the synchronous generator 4 and the inverter 6. The reactive power sharing amount determination unit 143 determines the reactive power sharing amount of each of the synchronous generator 4 and the inverter 6 from the reactive power supply amount.

  The control signal output unit 144 sends a control signal indicating the amount of reactive power shared by the inverter 6 to the inverter 6 via the output cable 12. The inverter 6 adjusts the reactive power amount according to the received control signal.

  FIG. 2 is a block diagram showing a hardware configuration of the system stabilizing device 14. The sensor input unit 141 is configured as an input device 201 that is an input interface through which various types of information are input. The control signal output unit 144 is configured as an output device 204 that is an output interface that outputs a control signal to the inverter 6. The reactive power supply amount determination unit 142 and the reactive power sharing amount determination unit 143 are realized by operating a program stored in the main storage device 203 while reading and writing necessary data from and to the secondary storage device 202 as needed.

<A-2. Operation>
As a method for determining the reactive power supply amount in the reactive power supply determining unit 142, for example, there is a method in which the sum of the reactive power amount of the synchronous generator 4 and the reactive power amount of the inverter 6 is used as the reactive power supply amount. Similarly to the AVR function of the synchronous generator 4, the reactive power supply amount may be calculated from the voltage value of the bus 1 that is system information.

The reactive power sharing amount determining unit 143 determines the reactive power sharing amount so that the power loss is minimized. Of the system information input by the sensor input unit 141, the voltage of the bus 1 to which the synchronous generator 4 is connected is V ₁ , the voltage of the stabilization target bus is V ₂ , and the active power output of the synchronous generator 4 is P _1. , The reactive power sharing amount of the synchronous generator 4 is Q ₁ , the active power output of the inverter 6 is P ₂ , the reactive power sharing amount of the inverter 6 is Q ₂ , and the impedance resistance component from the synchronous generator 4 to the interconnection point 3 Is R ₁ , R _{2 is} the resistance of the impedance from the inverter 6 to the connection point 3, η ₁ is the power generation loss rate of the synchronous generator 4, and η ₂ is the conversion loss rate of the inverter 6. The generation loss A ₁ , the transmission loss A ₂ , the generation loss B ₁ of the inverter 6, and the transmission loss B ₂ are expressed by the equations (1) to (4), respectively.

  Further, since the power loss C is the sum of the generation loss and the transmission loss of the synchronous generator 4 and the inverter 6, it is expressed as follows from the equations (1) to (4).

Here, in the present embodiment, the bus 1 to which the synchronous generator 4 is connected and the bus to be stabilized are the same, so V ₁ = V ₂ . Further, when the voltage V _{1 of the} bus 1 is high and the transmission loss is sufficiently small, only the sum of the generation loss can be expressed as the power loss by the following expression.

Since the sum of reactive power sharing amounts Q ₁ and Q ₂ becomes a constant value as reactive power supply amount Q, power loss C may be a function of Q ₁ as shown in equation (6), or Q ₂ It may be a function of

FIG. 3 shows the controllable range of the reactive power Q of the synchronous generator 4 in relation to the active power P. FIG. 3 shows a temperature limit F ₁ and a minimum excitation limit F ₂ for reactive power. The reactive power sharing amount Q ₁ of the synchronous generator 4 is set to a value in the region surrounded by the temperature limit F ₁ and the minimum excitation limit F ₂ in FIG. For example, the operating point is A in FIG.

FIG. 4 shows the controllable range of the reactive power Q of the inverter 6 in relation to the active power P. The control limit F3 of the reactive power Q shown in FIG. 4 is determined by the output limit of the inverter 6. Reactive power allocation amount Q ₂ of the inverter 6 is set to a value within a controllable range defined by the control limits F3. For example, the operating point is B in FIG.

The reactive power sharing amounts Q ₁ and Q ₂ are set to values at which the reactive power supply amount Q is within the controllable range shown in FIGS. 3 and 4 and the power loss C is minimized. For example, the reactive power sharing amounts Q ₁ and Q ₂ that minimize Equation (6) can be obtained by using the steepest descent method. This is because the condition (6) is unimodal, and the condition where the power loss C takes the minimum value and the condition where the differential value of the power loss C is close to 0 are the same.

Figure 5 is a flow chart of a method of calculating the reactive power sharing amount Q ₂ of the inverter 6 by the steepest descent method. The reactive power sharing amount determination unit 143 first sets an initial value of a search point (step S1). Although an arbitrary predetermined value can be set, for example, proportional distribution of the reactive power supply possible amount of the synchronous generator 4 and the inverter 6 is used. Next, a gradient vector at the search point for the power loss C, which is an evaluation function, is calculated (step S2). Next, it is determined whether or not the gradient vector obtained in step S2 is sufficiently small (step S3). If it is sufficiently small, the search point is taken as a solution and the search is terminated. If the gradient vector is not sufficiently small, the search point is moved in the direction of the gradient vector (step S4), and the process returns to step S2. Through the above search, reactive power sharing amounts Q ₁ and Q ₂ that reduce power loss can be calculated.

Here, the active power output P ₁ of the synchronous generator 4 is 2000 kW, the power generation loss η ₁ of the synchronous generator 4 is 20%, the active power output P ₂ of the inverter 6 is 8000 kW, and the power generation loss η ₂ of the inverter 6 is 6%. The reactive power supply amount Q = Q ₁ + Q ₂ necessary for system stabilization is set to 500 kW. Reactive power supply amount Q ₂ and power loss C of the inverter 6 is a relationship shown in FIG. By determining the reactive power sharing amounts Q ₁ and Q ₂ by the above-described method, the reactive power supply amount Q ₂ of the inverter 6 can be set to the optimum point indicated by the point C in FIG. 6, and the power loss is reduced. be able to.

By the way, the reactive power sharing amount determination unit 143 calculates the reactive power sharing amounts Q ₁ and Q ₂ of the synchronous generator 4 and the inverter 6, but the reactive power sharing amount control command is executed only to the inverter 6. The synchronous generator 4 can output reactive power sufficient to reach the reactive power supply amount Q in accordance with the reactive power output of the inverter 6 by its own AVR function. Accordingly, the command of the reactive power sharing amount to Q ₁ to a synchronous generator 4 is not necessary.

<A-3. Modification>
Incidentally, by determining in determining the reactive power allocation amount to Q ₁ synchronous generator 4, various temperature limit F1 and minimum narrower range than the control range of the reactive power determined by the excitation limit F2 (see FIG. 7), It is possible to leave room for controlling reactive power. That is, the operating point of the synchronous generator 4 is set to A ′ instead of A in FIG. In particular, when the reactive power supply amount Q is calculated from the sum of the reactive power supply amounts of the synchronous generator 4 and the inverter 6 in the reactive power supply amount determination process, when the voltage fluctuation of the system occurs, the stabilization operation is performed first. Since the synchronous generator 4 having the AVR function is started, by allowing the synchronous generator 4 to have a surplus power for reactive power control, it is possible to operate with the voltage stabilization capability maintained. Become.

<A-4. Effect>
The system stabilization device of the present embodiment is a system stabilization device that stabilizes the voltage of the bus 1 (system) to which the synchronous generator 4 is connected and the storage battery 5 is connected via the inverter 6. Necessary for stabilization based on the system information and the sensor input unit 141 (system information measurement unit) that measures system information including at least the power flow from the synchronous generator 4 to the bus 1 and the power flow from the inverter 6 to the bus 1 The reactive power supply amount determining unit 142 that determines the total reactive power amount of the synchronous generator 4 and the inverter 6 as the reactive power supply amount Q, and the reactive power based on the total power loss C of the synchronous generator 4 and the inverter 6 The reactive power sharing amount determination unit 143 that determines the reactive power sharing amounts Q ₁ and Q ₂ that are the sharing amounts of the supply amount Q for the synchronous generator 4 and the inverter 6 respectively, and the reactive power sharing amount Q ₂ of the inverter 6 And a control signal output unit 144 for sending the control signal shown to the inverter 6. Therefore, when supplying the reactive power necessary for stabilizing the system voltage, it is possible to realize an appropriate supply sharing between the synchronous generator 4 and the inverter 6 and reduce the power loss.

Moreover, reactive power sharing amount determining unit 143 in the control range of the active power P- reactive power Q characteristics determined by the temperature limit F1 and minimum excitation limit F2, determining the reactive power allocation amount to Q ₁ synchronous generator 4 it makes it possible to set the reactive power allocation amount Q ₁ can actually be controlled.

  Further, the reactive power sharing amount determination unit 143 determines the reactive power sharing amount of the synchronous generator 4 within a range narrower than the controllable range of the active power-reactive power characteristics, and generates the remaining power of the reactive power control by synchronous power generation. It can be operated in a state where it is held in the machine 4 and the voltage stabilization capability is maintained.

The system stabilization method of the present embodiment is a system stabilization method for stabilizing the voltage of the bus 1 (system) to which the synchronous generator 4 is connected and the storage battery 5 is connected via the inverter 6. (A) a step of measuring system information including at least the power flow flowing from the synchronous generator 4 to the bus 1 and the power flow flowing from the inverter 6 to the bus 1, and (b) synchronous power generation necessary for stabilization based on the system information. A step of determining the total value of reactive power amount of the machine 4 and the inverter 6 as the reactive power supply amount Q, and (c) a share of the reactive power supply amount Q based on the total power loss C of the synchronous generator 4 and the inverter 6 A step of determining the reactive power sharing amounts Q ₁ and Q ₂ for the synchronous generator 4 and the inverter 6, and (d) a step of sending a control signal indicating the reactive power sharing amount Q ₂ of the inverter 6 to the inverter 6. And. Therefore, when supplying the reactive power necessary for stabilizing the system voltage, it is possible to realize an appropriate supply sharing between the synchronous generator 4 and the inverter 6 and reduce the power loss.

In step (c), within the controllable range of the active power P- reactive power Q characteristics determined by the temperature limit F1 and minimum excitation limit F2, because it determines the reactive power allocation amount to Q ₁ synchronous generator 4, the actual it is possible to set the controllable reactive power sharing amount Q ₁ in.

In step (c), within a range narrower than the controllable range of the active power P- reactive power Q characteristic, because it determines the reactive power allocation amount to Q ₁ synchronous generator 4 actually controllable invalid it is possible to set the power sharing amount Q _1.

  In the present invention, the embodiments can be appropriately modified and omitted within the scope of the invention.

  1 busbar, 2 transmission line, 3 interconnection point, 4 synchronous generator, 5 storage battery, 6 inverter, 7 load, 8 wind power generator, 9A, 9B current transformer, 10 measuring transformer, 11A, 11B input cable, 12 output cable, 13 communication path, 14 system stabilizing device, 141 sensor input unit, 142 reactive power supply amount determining unit, 143 reactive power sharing amount determining unit, 144 control signal output unit, 201 input device, 202 secondary storage device , 203 Main storage device, 204 output device, 205 CPU.

Claims (6)

A system stabilizing device for stabilizing a voltage of a system to which a synchronous generator is connected and a storage battery is connected via an inverter,
A system information measuring unit that measures system information including at least a power flow flowing from the synchronous generator to the system and a power flow flowing from the inverter to the system;
Based on the grid information, a reactive power supply amount determining unit that determines a total value of reactive power amounts of the synchronous generator and the inverter necessary for the stabilization as a reactive power supply amount;
Based on the total power loss of the synchronous generator and the inverter, a reactive power sharing amount determining unit that determines a reactive power sharing amount that is a sharing amount of the reactive power supply amount for each of the synchronous generator and the inverter;
A control signal sending unit for sending a control signal indicating the reactive power sharing amount of the inverter to the inverter;
A system stabilization device comprising: The reactive power sharing amount determination unit determines the reactive power sharing amount of the synchronous generator within a controllable range of active power-reactive power characteristics determined by a temperature limit and a minimum excitation limit.
The system stabilizing device according to claim 1. The reactive power sharing amount determination unit determines the reactive power sharing amount of the synchronous generator within a range narrower than the controllable range of the active power-reactive power characteristics.
The system stabilizing device according to claim 2. A system stabilization method for stabilizing a voltage of a system (system) to which a synchronous generator is connected and a storage battery is connected via an inverter,
(A) measuring system information including at least a power flow flowing from the synchronous generator to the system and a power flow flowing from the inverter to the system;
(B) determining a total value of reactive power amounts of the synchronous generator and the inverter necessary for the stabilization based on the system information as a reactive power supply amount;
(C) determining a reactive power sharing amount for each of the synchronous generator and the inverter based on a total power loss of the synchronous generator and the inverter;
(D) sending a control signal indicating the amount of reactive power shared by the inverter to the inverter;
A system stabilization method comprising: The step (c) is a step of determining the reactive power sharing amount of the synchronous generator within a controllable range of active power-reactive power characteristics determined by a temperature limit and a minimum excitation limit.
The system stabilization method according to claim 4. The step (c) is a step of determining the reactive power sharing amount of the synchronous generator within a range narrower than the controllable range of the active power-reactive power characteristics.
The system stabilization method according to claim 5.

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