Power-distribution-system voltage control system, power-distribution-system voltage control method, and centralized voltage control apparatus

• US 10,345,842 B2
• Filed: 10/31/2011
• Issued: 07/09/2019
• Est. Priority Date: 10/31/2011
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Itaya, Nobuhiko
• Primary Examiner(s): Rutten, James D.
• Application Number:
  US14/354,610
• Publication Number:
  US 20140288725A1
• Time in Patent Office: 2,808 Days
• Field of Search: 700298
• CPC Class Codes: G05F 1/66 Regulating electric power
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02J 3/003 Load forecast, e.g. methods or systems for forecasting future load demand
• CPC Class Codes: H02J 3/12 for adjusting voltage in ac networks by changing a characteristic of the network load
• CPC Class Codes: Y02E 40/30 Reactive power compensation
• CPC Class Codes: Y02E 40/70 Smart grids as climate change mitigation technology in the energy generation sector
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/00 Systems supporting electrical power generation, transmission or distribution
• CPC Class Codes: Y04S 10/12 Monitoring or controlling equipment for energy generation units, e.g. distributed energy generation [DER] or load-side generation
• CPC Class Codes: Y04S 10/22 Flexible AC transmission systems [FACTS] or power factor or reactive power compensating or correcting units
• CPC Class Codes: Y04S 10/50 Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications

Abstract

A centralized voltage control apparatus calculates an optimum voltage distribution in a centralized control cycle period and determines, based on the relationship between the optimum voltage distribution and a proper voltage range, voltage upper and lower limit values for which a command is issued to each local voltage control apparatus taking into account voltage upper and lower limit margin amounts at respective points in a voltage control responsible range of the local voltage control apparatus for each local voltage control apparatus. The local voltage control apparatus adjusts, based on the voltage upper and lower limit values commanded from the centralized voltage control apparatus via a communication network, a control amount of a voltage control device every local control cycle shorter than the centralized control cycle period, to maintain the control voltage of the voltage control device between the voltage upper and lower limit values.

Claims

1. A power-distribution-system voltage control system comprising:

a distribution line of a high-voltage system from which a power distribution system of the high-voltage system is configured and to which a low-voltage system including a distributed power supply is connected;

a plurality of voltage control devices connected to the distribution line and configured to control a voltage of the distribution line;

local voltage control apparatuses connected to the voltage control devices, respectively, and configured to adjust a control amount of the voltage control devices every second cycle, such that a voltage value controlled by the voltage control devices is maintained within a range of a voltage upper limit value and a voltage lower limit value; and

a centralized voltage control apparatus including;

a load-and-power-generation-amount predicting unit configured to predict, every first cycle, a load and power generation amount distribution, which represents a difference between a pure load and a power generation amount at each point of the power generation system;

an optimum-voltage-distribution determining unit configured to determine the optimum voltage distribution in the first cycle period by performing a power flow calculation based on the load and power generation amount distribution predicted by the load-and-power-generation-amount predicting unit and by performing a search for a best solution to optimize a value of an evaluation function set for an evaluation item of the power distribution system; and

a voltage-upper-and-lower-limit-values determining unit, with respect to each of the local voltage control apparatuses, configured to;

select a minimum voltage-upper-limit margin amount out of voltage-upper-limit margin amounts, which are differences between optimum voltages obtained from the optimum voltage distribution within a voltage control responsible range, which is a range on the distribution line for which each of the local voltage control apparatuses is responsible in voltage control, and an upper limit value in a proper voltage range set in advance for the voltage responsible range;

select a minimum voltage-lower-limit margin amount out of voltage-lower-limit margin amounts, which are differences between the optimum voltages and a lower limit value in the proper voltage range in the voltage control responsible range;

determine, as the voltage upper limit value, a value obtained by adding the voltage-upper-limit margin amount to the optimum voltage of a voltage control device that is a control target of the local voltage control apparatus;

determine, as the voltage lower limit value, a value obtained by subtracting the voltage-lower-limit margin amount from the optimum voltage of the voltage control device; and

issue, via the communication network, a command to each of the local voltage control apparatuses setting the voltage upper limit value and the voltage lower limit value.

2. The power-distribution-system voltage control system according to claim 1, wherein the voltage-upper-and-lower-limit-values determining unit determines, with respect to each of the local voltage control apparatuses, the voltage upper limit value and the voltage lower limit value every first cycle and transmits the voltage upper limit value and the voltage lower limit value to each of the local voltage control apparatuses every first cycle.

3. The power-distribution-system voltage control system according to claim 2, further comprising a plurality of voltage and power flow measuring apparatuses that are each connected to the distribution line and are each connected to the centralized voltage control apparatus via the communication network and that each measure a voltage and a power flow of the distribution line and periodically transmit measurement information to the centralized voltage control apparatus, wherein

the load-and-power-generation-amount predicting unit predicts the load and power generation amount distribution based on the measurement information transmitted from the voltage and power flow measuring apparatuses.

4. The power-distribution-system voltage control system according to claim 3, wherein:

the centralized voltage control apparatus includes a load-and-power-generation-amount-predicted-values correcting unit configured to correct a predicted value of a load and power generation amount distribution in a current first cycle period based on a ratio of an actual value of a load and power generation amount distribution calculated based on the measurement information in a previous first cycle period immediately before the current first cycle period, and a predicted value in the period, and

the optimum-voltage-distribution determining unit determines the optimum voltage distribution based on a predicted value of a load and power generation amount distribution corrected by the load-and-power-generation-amount-predicted-values correcting unit.

5. The power-distribution-system voltage control system according to claim 2, wherein, when the voltage control device connected to the local voltage control apparatus is a transformer type, the voltage control responsible range is a range on the distribution line on a downstream side of the voltage control device and is a range before a next voltage control device appears on the distribution line.

6. The power-distribution-system voltage control system according to claim 2, wherein, when the voltage control device connected to the local voltage control apparatus is a reactive power control type and a voltage control device of a transformer type is present on an upstream side of the voltage control device, the voltage control responsible range includes a range that is on the distribution line on an upstream side of the voltage control device and is before the voltage control device of the transformer type appears, and a range that is on the distribution line on a downstream side of the voltage control device and is before a next voltage control apparatus appears on the distribution line.

7. The power-distribution-system voltage control system according to claim 2, wherein the first cycle is variable.

8. A centralized voltage control apparatus that is connected, via a communication network, to each of local voltage control apparatuses of a power distribution system that includes:

a distribution line of a high-voltage system from which the power distribution system of the high-voltage system is configured and to which a low-voltage system including a distributed power supply is connected;

a plurality of voltage control devices connected to the distribution line and configured to control a voltage of the distribution line; and

the local voltage control apparatuses connected to the voltage control devices, respectively, and configured to adjust a control amount of the voltage control devices every second cycle, such that a voltage value controlled by the voltage control devices is maintained within a range of a voltage upper limit value and a voltage lower limit value,

the apparatus including;

a load-and-power-generation-amount predicting unit that predicts, every first cycle, a load and power generation amount distribution based on a pure load and a power generation amount of the system;

an optimum-voltage-distribution determining unit that determines an optimum voltage distribution in the first cycle period by performing a power flow calculation based on the load and power generation amount distribution predicted by the load-and-power-generation-amount predicting unit and by performing a search for a best solution to optimize a value of an evaluation function set for an evaluation item of the power distribution system; and

a voltage-upper-and-lower-limit-values determining unit configured to;

select a minimum voltage-upper-limit margin amount out of voltage-upper-limit margin amounts, which are differences between optimum voltages obtained from the optimum voltage distribution within a voltage control responsible range, which is a range on the distribution line for which each of the local voltage control apparatuses is responsible in voltage control, and an upper limit value in a proper voltage range set in advance for the voltage responsible range;

select a minimum voltage-lower-limit margin amount out of voltage-lower-limit margin amounts, which are differences between the optimum voltages and a lower limit value in the proper voltage range in the voltage control responsible range;

determine, as the voltage upper limit value, a value obtained by adding the voltage-upper-limit margin amount to the optimum voltage of a voltage control device that is a control target of the local voltage control apparatus;

determine, as the voltage lower limit value, a value obtained by subtracting the voltage-lower-limit margin amount from the optimum voltage of the voltage control device; and

issue, via the communication network, a command to each of the local voltage control apparatuses for setting the voltage upper limit value and the voltage lower limit value.

9. A local voltage control apparatus:

connected to a voltage control device that is connected to a distribution line of a high-voltage system, from which a power distribution system of the high-voltage system is configured and to which a low-voltage system including a distributed power supply is connected, and controls a voltage of the distribution line, and

connected, via a communication network, to a centralized voltage control apparatus including;

a load-and-power-generation-amount predicting unit configured to predict, every first cycle, a load and power generation amount distribution, which represents a difference between the pure load and a power generation amount at each point of the power generation system;

an optimum-voltage-distribution determining unit configured to determine the optimum voltage distribution in the first cycle period by performing a power flow calculation based on the load and power generation amount distribution predicted by the load-and-power-generation-amount predicting unit and by performing a search for a best solution to optimize a value of an evaluation function set for an evaluation item of the power distribution system; and

a voltage-upper-and-lower-limit-values determining unit, with respect to each of the local voltage control apparatuses, configured to;

select a minimum voltage-upper-limit margin amount out of voltage-upper-limit margin amounts, which are differences between optimum voltages obtained from the optimum voltage distribution within a voltage control responsible range, which is a range on the distribution line for which each of the local voltage control apparatuses is responsible in voltage control, and an upper limit value in a proper voltage range set in advance for the voltage responsible range;

select a minimum voltage-lower-limit margin amount out of voltage-lower-limit margin amounts, which are differences between the optimum voltages and a lower limit value in the proper voltage range in the voltage control responsible range;

determine, as the voltage upper limit value, a value obtained by adding the voltage-upper-limit margin amount to the optimum voltage of a voltage control device that is a control target of the local voltage control apparatus;

determine, as the voltage lower limit value, a value obtained by subtracting the voltage-lower-limit margin amount from the optimum voltage of the voltage control device; and

issue, via the communication network, a command to each of the local voltage control apparatuses setting the voltage upper limit value and the voltage lower limit value, wherein;

the local voltage control apparatus adjusts a control amount of the voltage control device every second cycle, which is shorter than the first cycle, such that a voltage value controlled by the local voltage control device is maintained within a range of the voltage upper limit value and the voltage lower limit value that are updated every first cycle based on the command issued by the centralized voltage control apparatus, wherein the voltage upper and lower limit values are determined based on voltage limit margins computed using optimum voltages in the optimum voltage distribution.

10. A distribution grid system control system comprising:

a plurality of voltage control devices that are connected to different locations of a power distribution grid, each of which controls a voltage at the location connected thereto;

a local voltage control apparatus that controls, during a second cycle, at least one of the plurality of voltage control devices as a control target so that the voltage controlled by the control target is kept within a range between a first voltage upper limit and a second voltage lower limit; and

a centralized voltage control apparatus that issues, during a first cycle, a command to change the range between the first voltage upper limit and the second voltage lower limit to the local voltage control apparatus based on a third voltage upper limit, a fourth voltage lower limit and flow data of the power distribution grid, so that respective voltages at the different locations fall within a range between the third voltage upper limit and the fourth voltage lower limit, the centralized voltage control apparatus including;

a load-and-power-generation-amount predicting unit configured to predict, every first cycle, a load and a power generation amount distribution, which represents a difference between the pure load and the load and power generation amount at each point of the power generation system;

an optimum-voltage-distribution determining unit configured to determine the optimum voltage distribution in the first cycle period by performing a power flow calculation based on the load and power generation amount distribution predicted by the load-and-power-generation-amount predicting unit and by performing a search for a best solution to optimize a value of an evaluation function set for an evaluation item of the power distribution system; and

a voltage-upper-and-lower-limit-values determining unit, with respect to each of the local voltage control apparatuses, configured to;

select a minimum voltage-upper-limit margin amount out of voltage-upper-limit margin amounts, which are differences between optimum voltages obtained from the optimum voltage distribution within a voltage control responsible range, which is a range on the distribution line for which each of the local voltage control apparatuses is responsible in voltage control, and an upper limit value in a proper voltage range set in advance for the voltage responsible range;

select a minimum voltage-lower-limit margin amount out of voltage-lower-limit margin amounts, which are differences between the optimum voltages and a lower limit value in the proper voltage range in the voltage control responsible range;

determine, as the voltage upper limit value, a value obtained by adding the voltage-upper-limit margin amount to the optimum voltage of a voltage control device that is a control target of the local voltage control apparatus;

determine, as the voltage lower limit value, a value obtained by subtracting the voltage-lower-limit margin amount from the optimum voltage of the voltage control device; and

issue, via the communication network, a command to each of the local voltage control apparatuses setting the voltage upper limit value and the voltage lower limit value,

wherein the second cycle is shorter than the first cycle.