Patent Application
20140236367
The present invention refers to a control device conceived for use in hydraulic turbines in order to provide them with a high capacity of energy recovery for their facility, especially in supply networks.
Nowadays, in water supply networks, a wide range of regulating elements are available which allow adjusting the values of water flow rate and pressure, at different points in the network, with the aim of meeting the needs of users.
An example of this is the case of the regulating valves which are capable of causing a frictional loss pressure to maintain a constant pressure at the outlet regardless of the flow rate. These valves are generally used to reduce the pressure in certain parts of the network, which prevents breakages or decreases the level of leakages.
On numerous occasions it has been tried to use hydraulic turbines to replace said regulating valves and to achieve an electrical exploitation, the major drawback being the adjustment of the turbine to the flow rate values changing over time (since they depend on the users demand), further having to maintain a constant pressure at the outlet (pressure regulating valves) or at the inlet (pressure sustaining valves).
A typical case of this flow rate variability is constituted by urban potable water supply networks, in which the flow rate at nighttime is very low compared to the water demand at daytime consumption peaks.
The applicant knows the existence of numerous devices or means for adjusting the operation of a turbine depending on the circulating flow rate or pressure differential to be exploited. Such systems are usually mechanical and are present in high power turbines for hydroelectric exploitation. As an example of this, devices can be mentioned that are based on the orientation of the blades of the turbine, as it is the case with Kaplan turbines. These systems seek to maintain a high performance and a given rotation rate regardless of the flow rate to be processed by the turbine and pressure differential to be exploited, since they are usually equipped with synchronous generators that must rotate at a given speed to inject the energy into the grid.
These systems have the disadvantage of their high mechanical complexity, especially when they are to be installed in a micro-turbine for energy recovery in urban supply networks.
Similarly, the applicant knows the existence of hydraulic micro-turbines installable in supply networks which, however, do not have a suitable control system that allow them to adjust its operation to the required conditions of flow rate and pressure. Therefore, these turbines are not able to ensure a constant pressure at the outlet, but it depends on the circulating flow rate.
In an attempt to improve the hydraulic operation of these micro-turbines, assemblies have been carried out by placing a reducing valve at the outlet or a stopper at the inlet in order to thus achieve a level of constant pressure at the outlet regardless of the flow rate.
In this regard, it is noteworthy that although they achieve their objective hydraulically, they result very energy inefficient because they do not allow exploiting all the available pressure differential, part of which is lost by friction in the regulating valve, the stopper or any other mechanical element.
In turn, and for a completely opposed aspect of such systems, the applicant knows the so-called “regenerative braking systems” used in various fields of industry, which allow regulating the braking torque of a generator and therefore the generated electrical power.
Typically, such regenerative braking systems are connected to generators or servomotors of the brushless type.
Practical examples of this can be found in hybrid vehicles (which recover energy from braking to recharge batteries), in new generation elevators, in servomotors for braking of shafts, etc.
The technical problem solved herein is to increase the overall energy performance in supply networks such as networks of potable water, filtered irrigation water, etc.
To solve this technical problem it is described a control device for hydraulic turbines that, connected with a micro-turbine, allows an electronic control and a regenerative braking of the micro-turbine.
In fact, the device is provided to regulate the braking torque exerted by the generator on the turbine shaft, to which it is integrally attached, so as to maintain a constant pressure at the inlet or outlet of the turbine regardless of the water flow rate circulating through it. Thus, it is achieved that the turbine behaves like a pressure regulating valve, maintaining a constant level of pressure at the inlet, with the further advantage of being able to generate electrical energy by replacing the existing pressure regulating or sustaining valves.
More specifically, the control device for hydraulic turbines is configured to adjust the resistant torque provided by the generator to the movement of the impeller of a hydraulic turbine so that a stable pressure is set at the inlet or outlet regardless of the circulating flow rate, and to adjust the electrical energy produced by the turbine to achieve the desired hydraulic behavior, which is characterized by comprising first control means and second power means; wherein said first means are connected to means for detecting the pressure at the inlet and at the outlet, and a flow-meter for obtaining the circulating flow rate, and to means for measuring the power of the turbine; all this, in such a way that said first control means act on the second power means for causing the application of the braking torque necessary to maintain a stable set-point value in the turbine.
In the following, a series of drawings is described very briefly which help to better understand the invention and which are expressly related to an embodiment of said invention which is presented as a non-limiting example thereof.
As previously explained, the device of the invention allows a new control strategy based on which the turbine exploits at any time the maximum hydraulic energy available in the network, further ensuring a stable hydraulic behavior despite the flow rate variations that occur in supply networks, since it depends on the needs of users.
The use of a regenerative braking system in hydraulic turbines permits adjusting the resistant torque provided by the generator to the movement of the impeller, so that a stable pressure level can be ensured at the inlet or outlet of the turbine regardless of the flow rate circulating through it and, therefore, adjusting the generated electrical energy to the available hydraulic energy.
As shown in the attached figure, the device of the invention comprises first control means (100) and second power means (200).
The first control means (100), in a first embodiment, comprise a PLC that receives signals of pressure at the inlet (Pi), pressure at the outlet (Po), circulating flow rate (Q) obtained through a flow-meter (1) and generated electric power, which is obtained via a network analyzer (2) connected directly to the power signal of the turbine (3).
The first control means (100) presents a PID structure.
Appropriate orders can be sent through the control means (100) to the second power means (200) to apply the braking torque necessary to maintain a stable set-point value. Therefore, it is configured to adjust the electrical energy produced by the turbine (3) to achieve the desired hydraulic behavior.
Based on the received signals, the first control means (100) are configured to operate in one of the following operation modes:
a) a first mode, wherein the turbine (3) regulates the pressure; wherein the first control means (100) are configured to calculate the braking torque necessary to maintain the pressure set-point at the outlet or at the inlet of the turbine (3) regardless of the demanded flow rate, having a hydraulic behavior equal than a pressure regulating valve.
b) a second mode with the turbine (3) at maximum power, wherein the first control means (100) are configured to calculate the braking torque with the maximum generated power without ensuring a constant pressure, since it will depend on the demanded flow rate (Q).
c) a third mode with the turbine (3) at maximum performance, wherein the first control means (100) are configured to determine the braking torque necessary for the yield to be maximum, without ensuring a constant pressure value, maximizing the ratio between the generated electric power and the available hydraulic power; and,
d) a fourth mode with the turbine (3) regulating the flow rate (Q), wherein the control means (100) are configured to set the braking torque necessary to maintain a constant flow rate set-point regardless of the pressure upstream (Pi) or downstream (Po) of the turbine (3).
The second power means (200), which are directly connected to the generator of the turbine (3), are responsible for adjusting the generated electrical energy to charge a battery or for injection into the grid Likewise, they are responsible for exciting the windings of the stator of the generator according to the order of the first control means (100), so that the resistant torque therein is adequate to maintain the set-point.
On a practical level, the second power means (200) can be implemented by a driver (201) based on a bridge of thyristors or IGBT antiparallel configured and synchronized by means of the signals received by the first control means (100), allowing a controlled passage of current generated by the generator itself, which could be of the “brushless” type, and so regulate the braking torque exerted by it on the impeller of the turbine.
In the attached figure, it can be seen how the generating turbine (3) is installed in the duct (4), and is placed in an underground chamber or a valves room along with the measuring equipment [pressure sensors (Po, Pi) and flow-meter (1)]. Thus, a pressure sensor is placed at the inlet (Pi) and another at the outlet (Po) of the turbine (3), while the flow-meter (1) can be placed at the inlet or outlet thereof.
The wiring of signals from the measuring equipment [the network analyzer (2)], as well as the wiring of power from the generator of the turbine (3), conduct it to the control device (100, 200), which may be located in the same enclosure or in a separate enclosure.
The power output of the control device (100, 200), which can be monitored with a network analyzer (2), is connected to the energy receiving system (5), which may be an inverter for injection of electricity into the network, an equipment of battery charging, a particular facility for self-consumption, or any other system which can exploit electrical energy.
By controlling the regenerative braking, the turbine (3) can operate at different rotation rates depending on the conditions of flow rate (Q) and available hydraulic jump.
| Number | Date | Country | Kind |
|---|---|---|---|
| P 201100746 | Jun 2011 | ES | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/ES2012/000178 | 6/25/2012 | WO | 00 | 3/26/2014 |
