WO2019107375A1

WO2019107375A1 - Hydroelectric system and control method

Info

Publication number: WO2019107375A1
Application number: PCT/JP2018/043646
Authority: WO
Inventors: 伊藤　隆志
Original assignee: Ntn株式会社
Priority date: 2017-11-28
Filing date: 2018-11-27
Publication date: 2019-06-06
Also published as: JP6955978B2; KR20200092993A; KR102639063B1; JP2019097367A

Abstract

A hydroelectric system is provided which can perform suitable output power control without prior measurement, and which, even when a stall state has occurred, allows recovery from the stall state to a normal power generating state by reducing or releasing the generator load, and which can generate a large amount of power and can prevent hunting of power control. This hydroelectric system is provided with a water wheel (1), a generator (3), and a control device (4). The control device (4) performs basic control with MPPT control, etc. The control device (4) determines a stall state of the water wheel (1) with a stall determination means (22), and, at the time of a stall state, reduces or releases the load power of the generator (3) by means of a load reducing/releasing means (23). In order to determine stalling, a stalling determination curve (A) which determines a stall state when the differential power has risen and/or the differential rotation speed has decreased, and a recovery determination curve (B) which determines a non-stall state when the differential power has decreased and/or the differential rotation speed has risen, and the area between the curves (a, b) is a stall boundary region (C) which constitutes a hysteresis region.

Description

HYDRO POWER GENERATION SYSTEM AND CONTROL METHOD

Related application

This application claims the priority of Japanese Patent Application No. 2017-227737 filed on November 28, 2017, which is incorporated by reference in its entirety.

The present invention relates to a hydroelectric system and control method having a function of determining a stall state of a hydroelectric generator and returning it to a normal state.

A hydroelectric generator is a system that uses kinetic energy of flowing water for power generation. The hydroelectric power generation device mainly includes: a water turbine that receives a flow of water; a generator that is connected to the water turbine and converts the rotation energy into electrical energy; and a controller that controls the output of the generator and the water turbine. Prepare.

Since the power extracted from the generator changes with the flow velocity, the controller measures the flow velocity, the rotational speed of the water turbine, or the generated voltage of the generator to determine the optimal power extracted from the generator, and generates the power of the generator. Control to match the power and the optimum value.

For this purpose, it is necessary to install a hydroelectric generator in the water channel in advance, measure the flow velocity, the generated power, and the power generation characteristics, set optimum values, and create the table characteristics by a control map or the like. Therefore, cost increase factors such as measurement work occur until the operation of the hydroelectric system.

In order to eliminate the prior measurement and the setting operation of the optimum value, there has been proposed a method of controlling hydroelectric power generation by maximum power point tracking control called MPPT control according to hill climbing or the like (for example, Patent Document 1). MPPT control is also used in wind power generation (for example, Patent Document 2).

JP, 2016-185006, A Unexamined-Japanese-Patent No. 2010-200533

However, it may be difficult to apply the MPPT control to the hydroelectric power generation control device, since the rotational speed of the water turbine may decrease and the power generation may also decrease.

In the Patent Document 2, although MPPT control in wind power generation, control to cope with a stall is proposed. That is, every time when the optimum operating point of the generator is sought by MPPT control, the time derivative of the output voltage or the time derivative of the output current is calculated, and the output power at the operating point and the time derivative of the calculated output power Stall is determined based on whether or not the relation of (1) satisfies the stall boundary condition. When it is determined that a stall occurs, the load on the generator is released or reduced.

However, when the stall boundary condition is not satisfied by releasing or reducing the generator load, when the load returns to the original value, the stall boundary condition is immediately met, and the power limit is turned on and off. Hunting may occur, which is repeated.

The present invention solves the above-mentioned problems, and an object thereof is to perform appropriate output power control without performing prior measurement, and to reduce or release the load of the generator even in a stall state. It is an object of the present invention to provide a hydroelectric power generation system and control method which makes it possible to return from a stalled state to a normal power generation state, obtain a large amount of generated power, and prevent hunting of power control.

Hereinafter, in order to facilitate understanding, for convenience, reference will be made to the reference numerals of the embodiments.

The hydroelectric power system according to the present invention comprises a water turbine 1 rotating in water, a generator 3 converting the rotational energy of the water turbine 1 into electrical energy, and adjusting the load power of the generator 3 to adjust the rotational speed of the water turbine 1 A hydraulic power generation system comprising a control device 4 for controlling
The control device 4 is
Power past present value detecting means 16 for detecting the output power past value and the output power present value of the generator 3;
Power past present value storage means 17 for storing the detected output power past value and the output power present value;
Rotational speed past present value detecting means 18 for detecting the rotational speed past value and rotational speed present value of the generator 3;
Rotational speed past current value storage means 19 for storing the detected rotational speed past value and the rotational speed current value;
Difference power calculating means 20 for calculating a difference power between the output power past value and the output power present value;
Differential rotation number calculation means 21 for calculating a difference rotation number between the output rotation number past value and the output rotation number current value;
Stall determination means 22 for determining the stall state or non-stall state of the water turbine from the differential power and the differential rotation speed;
A load reducing / releasing means 23 for reducing or releasing the load of the generator 3 when the stall determining means 22 determines that the vehicle is in a stall state;
A determination curve indicating the relationship between the difference power and the difference rotational speed between a stall determination region A in which the stall determination unit 22 determines that the vehicle is in a stalled state and a non-stall determination region B in which the stall determination unit 22 determines that the vehicle is not in a stalled state. The judgment curves a and b are classified according to a and b, and when the differential power decreases with the stall judgment curve a for determining a stall state when the differential power increases and / or the differential rotational speed decreases. And / or a return determination curve b for determining a non-stall state when the differential rotation speed increases, and a stall boundary area C is configured as a hysteresis area between the curves a and b.

According to this configuration, the control device 4 basically monitors the generated power and the like, and controls the number of rotations of the water turbine 1 by controlling the output power in accordance with a defined control rule. During this time, the stall determination unit 22 determines the stall state or the non-stall state of the water turbine 1 from the differential power and the differential rotation speed, and when it is determined that the stall state is present, the load reducing / releasing means 23 The load power of the generator 3 is reduced or released. As described above, when the stall of the water turbine 1 occurs, the load power can be reduced or released, so that the stall state can be returned to the normal power generation state, and a large generated power can be obtained. Since the determination of the stall condition is performed based on the difference power and the difference rotational speed between the present and the past, appropriate determination can be performed. Further, since the stall boundary area C is provided as the hysteresis area, hunting of the power control by the stall determination is prevented. The rotational speed is a rotational speed per unit time, in other words, a rotational speed.

The control device 4 includes an MPPT control means 6 for controlling the maximum power operating point following the output fluctuation of the generator 3, and the stall judging means 22 controls the water wheel every time the maximum power operating point is searched. The stall condition or non-stall condition of 1 may be determined, and the load reducing / releasing means 23 may reduce or release the load of the generator 3 as necessary.

According to the MPPT control in which the maximum power operating point is followed and controlled, efficient power generation can be performed even if the preliminary measurement work of the flow velocity and the turbine rotational speed at the site where the turbine 1 is installed is omitted. However, when MPPT control is applied to a hydroelectric power generation system, it can not be restored to the normal state when it is in a stall state where the rotational speed of the water turbine 1 is reduced and the generated power is also reduced. is there. According to this hydroelectric power generation system, the stall condition is determined, and the load power is reduced or stopped during the stall condition, so that recovery from the stall condition can be performed, and the generated power reduction due to the stall does not occur largely. , MPPT control can be performed efficiently.

The control method of the hydroelectric power generation system according to the present invention includes a hydraulically rotating water turbine 1, a generator 3 for converting rotational energy of the water turbine 1 into electric energy, and adjustment of load power of the generator 3 to rotate the water turbine 1 A method of controlling a hydroelectric power generation system comprising a controller 4 for controlling the number of
A difference power calculation process (S6) for obtaining a difference power between the past value and the current value of the output power of the generator 3;
A differential rotation number calculating step (S5) for obtaining a differential rotation number between a past value and a current value of the rotation number of the generator 1;
A stall determination step (S6) of determining a stall state or a non-stall state depending on whether or not the relationship between the differential power and the differential rotational speed satisfies a predetermined stall boundary condition;
And a load reducing / releasing process (S7) for reducing or releasing the load of the generator (3) when it is determined in the stall determination process (S6) that the vehicle is in a stall state.
These processes are repeated for each control cycle of the control device 4,
The stall boundary condition is determined by determination curves a and b indicating the relationship between the difference power and the difference rotational speed, and a stall determination region A determined to be a stall condition and a non-stall determination region determined to be a non-stall condition B is divided by the determination curves a and b, and the determination curve decreases the difference between the stall determination curve a determined as a stall condition when the difference power increases and / or the difference rotational speed decreases and the difference power decreases And a return determination curve b for determining a non-stall state when the differential rotational speed increases, and a stall boundary area C is formed as a hysteresis area between the curves a and b.

According to this control method, as described above for the hydroelectric power generation system, even if a stall state occurs, the normal power generation state can be restored, and it is possible to obtain large generated power. Further, since the stall boundary area C is provided as the hysteresis area, hunting of the power control by the stall determination is prevented.

The control device 4 includes an MPPT control means 6 for following and controlling the maximum power operating point with respect to the output fluctuation of the generator 3, and the difference power calculation process every time the operating point is searched for by the following control. (S6), the differential rotation speed calculation process (S5), the stall determination process (S7), and the load reduction / release process (S8) may be repeated as necessary.

According to the MPPT control, efficient power generation can be performed even if the advance measurement work of the flow velocity and the turbine rotational speed on site is omitted. However, the control may not be able to return to the normal state when the engine is stalled. In this regard, according to this method, the stall condition is determined, and the load power is reduced or stopped in the stall condition, so that the stall condition can be recovered and MPPT control is performed without causing a large reduction in generated power due to stall. Efficient control can be performed.

Any combination of the at least two configurations disclosed in the claims and / or the description and / or the drawings is included in the present invention. In particular, any combination of two or more of the claims is included in the present invention.

The invention will be more clearly understood from the following description of the preferred embodiments with reference to the accompanying drawings. However, the embodiments and the drawings are for the purpose of illustration and description only and are not to be taken as limiting the scope of the present invention. The scope of the invention is defined by the appended claims. In the accompanying drawings, the same reference numerals in multiple drawings indicate the same or corresponding parts.
BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the outline of the hydraulic power generation system which concerns on one Embodiment of this invention. It is a block diagram which shows the conceptual structure of the hydraulic power generation system of FIG. It is a stall threshold value control graph which becomes a reference example of a stall judging field and a non-stall judging field. It is the stall threshold value control graph which shows the stall determination area | region used by the hydraulic power generation system of FIG. 1, a non-stall determination area | region, and a stall boundary area | region. It is a flowchart which shows the procedure of the control method which the hydraulic power generation system of FIG. 1 performs. It is a schematic explanatory drawing of the other example of the hydraulic power generator used with the hydraulic power generation system of FIG.

An embodiment of the present invention will be described with reference to the drawings. This hydroelectric power generation system is an example of a horizontal axis (propeller type) hydroelectric generator. The water turbine 1 is rotated by the kinetic energy of the water flowing through the water channel (not shown), and the main shaft 2 of the water turbine 1 rotates the generator 3. The generator 3 is a three-phase synchronous generator using, for example, a permanent magnet, and is connected to the main shaft 2 by a coupling (not shown) or the like. A speed increaser 25 may be provided between the main shaft 2 and the generator 3 as in the example of FIG.

When a load is connected to the generator 2 to consume the output, torque is applied to the water turbine 1 from the generator 3, and the rotation of the water turbine 1 is braked. When the load power is increased, the rotation speed of the water wheel 3 is decreased, and when the load power is decreased, the rotation speed of the water wheel 3 is increased. A load circuit is connected as a load of the generator 3 via the control device 4. The control device 4 increases or decreases the torque of the generator 3 according to the flow velocity, and controls the water turbine to rotate at an optimal rotation speed. A DC / DC converter, an inverter or the like is used for the control device 4. The load circuit 5 is an electrical device or a load system.

FIG. 2 shows a specific example of the control device 4. The control device 4 includes a main circuit unit 6 that supplies the generated power of the generator 3 to the load circuit 5 and a control circuit unit 7 that controls the main circuit unit 6 and further includes a battery 8 that stores the generated power. ing. The main circuit portion 6 includes a rectifier 9, a converter 10, an ammeter 11, a voltmeter 24, and a switching means 12 sequentially interposed between the battery 8 and the generator 3.

The rectifier 9 is a device that rectifies the three-phase AC power generated by the generator 3 into a direct current, and is configured by a half bridge circuit of a semiconductor switching element. Converter 10 comprises, for example, a boost chopper. Alternatively, converter 10 may be a buck chopper. The switching means 12 is means for switching whether or not the rectified DC power is supplied to the battery 8 by turning on and off. The switching means 12 may be a semiconductor switching element or a contact switch. The switching means 12 can be switched on and off by a control signal output from the gate circuit 15.

The battery 8 and the load circuit 5 are in parallel, and can charge the load circuit 5 while charging the power generated by the generator 3 to the battery 8. In the main circuit unit 6, the battery 8 and the load circuit 5 are connected in parallel to the output side of the generator 3, so the output voltage becomes substantially constant. Therefore, the output power of the generator 3 can be adjusted by adjusting the duty ratio of the output current of the converter 10 by opening and closing the switching means 12.

The control circuit unit 7 is composed of a computer or the like, and in this example, performs basic control by the MPPT control means 13 which is a basic control means, and performs control for the stall of the water wheel 1 by the stall response control means 14. The MPPT control means 13 and the stall correspondence control means 14 both control the switching means 12 under the control of the gate circuit 15 to adjust the output power. The control circuit unit 7 may perform basic control by basic control means that adopts a control method different from the MPPT control means 13.

The MPPT control means 13 changes the operating point of the generator 3 so as to always follow the maximum output operating point in control with respect to the fluctuation of the output power of the generator 3, thereby the maximum output from the generator 3 It is a means to control taking out. The maximum output operating point is an operating point at which the output to the load circuit 5 is maximum among the operating points obtained for each sampling by the MPPT control means 13. The power at the operating point is detected from the measurement values of the ammeter 11 and the voltmeter 24.

The stall handling control means 14 includes a power past present value detecting means 16, a power past present value storage means 17, a rotational speed past present value detecting means 18, a rotational speed past present value storage means 19, a difference power calculating means 20, a difference rotational speed The calculation unit 21, the stall determination unit 22, and the load reduction / release unit 23 are provided. The stall handling control means 14 repeatedly performs a series of stall determination processing. In this embodiment, whenever the operating point is searched for in the MPPT control, the determination of the stall by the stall determining unit 22 and the processing by the load reducing / opening unit 23 as necessary are performed.

The power past present value detecting means 16 detects the output power past value and the output power present value of the generator 3. The output power present value is the output power at the time of sampling for each of the series of stall determinations, that is, in this example, the most recent sampling among sampling performed every time the operating point is searched by the MPPT control. The output power past value is, for example, the output power at the time of sampling one time before the most recent sampling. The output power past value may be an average value of output powers of a plurality of recent samplings. The output power to be sampled is, for example, a value obtained by multiplying the current obtained by the ammeter 11 by the voltage obtained by the voltmeter 24. The current obtained by the ammeter 11 may be multiplied by a constant voltage which is the voltage of the battery 8. A power past present value storage means 16 may be provided with a power meter (not shown) for detection, and is means for storing the detected output power past value and output power present value of the generator 3.

The rotational speed past present value detection means 18 is a means for detecting the rotational speed past value and the rotational speed current value of the generator 3 from a rotation detector (not shown) provided in the generator 3. The rotational speed past value and the rotational speed current value may be the rotational speed at the time of the most recent sampling and the previous sampling, as with the output voltage past value and the output voltage current value. The rotational speed past present value storage means 19 is means for storing the detected rotational speed past value and rotational speed current value of the generator 3.

The difference power calculation means 20 is a means for calculating the difference power ΔP of the output power past value of the generator 3 and the output power present value stored in the power past present value storage means 19. The differential rotational speed computing means 13 is a means for computing the differential rotational speed ΔN of the output rotational speed past value of the generator 3 and the output rotational speed present value stored in the rotational speed past present value storage means 19.

The stall determination unit 22 is a unit that determines whether or not the vehicle is in a stall condition based on whether or not a stall boundary condition defined by the difference power ΔP and the difference rotational speed ΔN is satisfied. Specifically, as shown in FIG. 4, a judgment curve a showing the relationship between the difference power ΔP and the difference rotation speed ΔN, as shown in FIG. It is divided by b. The determination curves a and b are not one determination curve d as in the example of FIG. The stall determination curve a is a curve determined to determine that a stall occurs when the difference power ΔP is increased and / or when the differential rotation speed ΔN is decreased. The return determination curve b is a curve that is determined to determine non-stall when the difference power ΔP decreases and / or when the difference rotation speed ΔN increases. A stall boundary region C of the hysteresis region is a region between the two curves a and b.

The load reducing / releasing means 23 is means for reducing or releasing the load power of the generator 3 when the stall determining means 22 determines that the vehicle is stalled. Specifically, the load reducing / releasing means 23 reduces the duty of the converter 10 by opening / closing the switching means 12 through the gate circuit 15, or keeps the switching means 12 open to reduce or release the load power. Do.

With reference to FIG. 5, the flow of the stall corresponding control in the hydraulic power generation system of the above configuration will be described. This figure shows the flow of control processing performed by the stall corresponding control means 14 of FIG. The control process of FIG. 6 is repeated each time the MPPT control goes to search for an operating point.

First, the rotational speed past value and rotational speed current value of the generator 3 are detected in the rotational speed detection process (S1), and the output electric power past value and output electric power current value of the generator 3 are detected in the power detection process (S2) I do. The detected rotational speed past value (previous value N0) and rotational speed present value (N1), and output power past value (previous value P0) and output power present value (P1) are respectively the rotational speed storing process ( In the step S3) and the power storage process (S4), the rotational speed past present value storage means 19 and the power past present value storage means 17 are stored. The stored contents are updated every control cycle.

A differential rotational speed calculation step (S5) calculates the differential rotational speed ΔN between the stored rotational speed past value (previous value N0) and the rotational speed current value (N1). That is, ΔN = N0−N1 is calculated. A difference power calculation step (S6) calculates the difference power ΔP between the stored output power past value (previous value P0) and the output power present value (P1). That is, ΔP = P0−P1 is calculated.

In the stall determination step (S7), the stall determination means 22 determines whether or not the calculated differential rotation speed ΔN and the difference power Δ satisfy the predetermined stall boundary condition.

If it is determined that the vehicle has not stalled, the control process ends. When it is determined that the engine is stalled, in the load reducing / releasing process (S8), the load reducing / releasing means 23 extends the time for opening the switching means 12 via the gate circuit 15 or keeps the opening open. Reduce or release the load power of machine 3

When the maximum power point is followed by the MPPT control by the control device 4 in the hydroelectric power generation system, the water turbine 1 may be in a stalled state, which causes a significant decrease in the generated power. On the other hand, as described above, by determining the stall condition with the control device 4 and reducing or releasing the load power, it is possible to bring about the normal power generation state. This makes it possible to obtain a large amount of generated power.

When the stall condition is determined as described above, if the stall determination region A and the non-stall determination region B determined to be non-stall are divided by one determination curve d as shown in FIG. Then, after the load power is reduced or released and the non-stall state is reached, there is no significant change in the flow velocity of the water flow and the like.

On the other hand, in this embodiment, as the stall boundary condition, as shown in FIG. 4, a stall judgment area A for judging as stall and a non-stall judging area B for judging as non-stall It is divided by two judgment curves a and b which show the relation of. That is, when the differential power decreases and / or the differential rotational speed increases, the determination curve determines that the vehicle is in the stall state when the differential power increases and / or the differential rotational speed decreases. And a return determination curve b for determining a non-stall state. A stall boundary area C is formed as a hysteresis area between these curves.

Whether it is judged by the stall judgment curve a or by the return judgment curve b is stored in the previous judgment (previous control cycle) using a flag etc. If the previous time is a non-stall state, the determination is made using the stall determination curve a, and if the previous time is a stall state, it is determined using the return determination curve b.

If it is determined that the vehicle has entered the stall determination area A after the stall determination curve a and is once determined to be stalled, the stall determination is performed even if the stall boundary area C is again exceeded the stall determination curve a due to reduction or release of the load power. When the state is maintained and the return judgment curve b is exceeded to enter the non-stall judgment region B, it is judged that the vehicle is in the non-stall state. Therefore, hunting of the stall determination is prevented and control is stabilized.

As described above, although the preferred embodiments have been described with reference to the drawings, various additions, modifications or deletions can be made without departing from the spirit of the present invention. Therefore, such is also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Water wheel 3 ... Generator 4 ... Control apparatus 16 ... Electric power past present value detection means 17 ... Electric power past present value storage means 18 ... Rotation speed past present value detection means 19 ... Rotation speed past present value storage means 20 ... Difference electric power calculation Means 21 ... Differential rotational speed calculation means 22 ... Stall determination means 23 ... Load reduction / release means

Claims

With a hydraulically rotating water turbine,
A generator that converts the rotational energy of this water turbine into electrical energy,
And a control device for adjusting the load power of the generator to control the rotational speed of the water turbine,
The controller is
Power past present value detecting means for detecting the output power past value and the output power present value of the generator;
Power past present value storage means for storing the detected output power past value and the output power present value;
Revolution number past present value detecting means for detecting the revolution number past value and revolution number present value of the generator;
Rotational speed past current value storage means for storing the detected rotational speed past value and the rotational speed current value;
Difference power calculating means for calculating a difference power between the output power past value and the output power present value;
Differential rotation number calculation means for calculating a difference rotation number between the output rotation number past value and the output rotation number current value;
Stall determination means for determining a stall state or a non-stall state of the water turbine from the differential power and the differential rotational speed;
A load reducing / releasing means for reducing or releasing the load of the generator when the stall determining means determines that the vehicle is in a stall state;
A stall determination region in which the stall determination unit determines that the vehicle is in a stall state and a non-stall determination region in which the stall determination unit determines that the vehicle is not in a stall state are divided by a determination curve that indicates the relationship between the differential power and the differential rotation speed. The judgment curve includes a stall judgment curve for judging as a stall state when the difference power rises, and a return judgment curve for judging as a non-stall state when the difference power falls, A stall boundary area is configured as a hysteresis area,
Hydroelectric system.
The hydroelectric power generation system according to claim 1, wherein the control device comprises an MPPT control means for following and controlling the maximum power operating point with respect to the output fluctuation of the generator, each time the maximum power operating point is searched, The hydroelectric power generation system, wherein the stall determination means determines the stall state or non-stall state of the water turbine, and the load reducing / releasing means reduces or releases the load of the generator as necessary.
With a hydraulically rotating water turbine,
A generator that converts the rotational energy of this water turbine into electrical energy,
And a controller for adjusting the load power of the generator to control the rotational speed of the water turbine.
A difference power calculation process for obtaining a difference power between a past value and a current value of output power of the generator;
A differential rotational speed calculation process of obtaining a differential rotational speed between a past value and a current value of the rotational speed value of the generator;
A stall determination step of determining a stall state or a non-stall state depending on whether or not the relationship between the difference power and the difference rotational speed satisfies a predetermined stall boundary condition;
And a load reducing / releasing process for reducing or releasing the load of the generator when it is determined in the stall determination process that the vehicle is in a stall state.
These processes are repeated for each control cycle of the control device,
The stall boundary condition is determined by a determination curve indicating the relationship between the difference power and the difference rotational speed, and a stall determination area determined to be a stall state and a non-stall determination area determined to be a non-stall state are the The judgment curve is divided by a judgment curve, and the judgment curve includes a stall judgment curve which judges as a stall state when the difference power rises, and a return judgment curve which judges as a non-stalling state when the difference power falls. The stall boundary area is configured as a hysteresis area in
Control method of hydroelectric power generation system.
4. The control method of a hydroelectric power generation system according to claim 3, wherein said control device comprises an MPPT control means for following and controlling a maximum power operating point with respect to an output fluctuation of said generator, and said operating point is controlled by said tracking control. A control method of a hydroelectric power generation system, in which the difference power calculation process, the difference rotation speed calculation process, the stall determination process, and the load reduction / release process are repeated as needed each time a search is made.