JP2796298B2 - Variable speed pumping plant - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable speed pumping plant, and more particularly to a variable speed pumping plant having a configuration in which an upstream or downstream pipe is shared with another pump. [Prior Art] It is generally considered that a pump-turbine cannot avoid a hump characteristic (a characteristic that partially satisfies dH / dQ> 0) as shown by a dotted line in FIG. 5 on the high head side. The operation in this part is not only unstable and accompanied by vibration noise, but also because the flow rate Q appears as a trivalent function under the same head, the flow rate Q suddenly changes and also jumps, causing an abnormal water hammer phenomenon. There is.
The degree of depression of the hump characteristic varies depending on the guide blade opening degree as shown in FIG. 6, but even if a distinct depression characteristic does not occur, the flow in the runner becomes unstable, and the same problem occurs. It is said that the reason for this is that when the flow rate is small, the water flow is deviated in the radial direction as shown in FIGS. Also, in such a state, the flow separates from the blade surface, resulting in a so-called stall state. By the way, in JP-A-62-186069, when increasing the load of the variable speed pumping device, first increase the output of the driving device and increase the rotation speed so that the operating point of the pump turbine does not transiently fall into the above-described hump characteristic. He said that the guide vanes should be raised afterwards. It is disclosed that when the load is reduced, the closing operation of the guide blades and the lowering operation of the rotation speed are performed simultaneously, but the closing of the guide blades is completed earlier than the lowering of the rotation speed.
However, when the upstream or downstream pipeline of the pump turbine is shared with another hydraulic machine (that is, when a plurality of hydraulic machines are installed branching from the same pipeline), any of the other hydraulic turbines is used. If the hydraulic machine changes its operation state and changes its flow rate, a water hammer occurs in this hydraulic machine, and this is transmitted to the pump-turbine under consideration through the shared pipeline, so that the influence is always exerted. In particular, when the head H is swung upward, there is a possibility that a drop in the hump characteristic may occur even if the variable speed water pumping device can be completely controlled by itself. Further, in Japanese Patent Application Laid-Open No. 61-149583, when the pump is started, that is, when the pump turbine is shifted from the shut-off state to a full-scale variable speed pumping operation with a desired load, a step is taken in accordance with the degree of opening of the guide vanes gradually opened. A pump starting method is disclosed in which the rotational speed command is increased in a manner as described above, and finally an appropriate rotational speed and an appropriate guide blade opening at the desired load are achieved. However, this known example does not mention a control method after the full-scale variable speed pumping operation is started. Further, Japanese Patent Application Laid-Open No. 61-175271 discloses a method in which when the water level difference between the upper pond water level and the lower pond water level exceeds a predetermined value, the rotation speed is increased according to the overshoot and corrected. However, it is completely unprotected that a backflow occurs in the runner due to a temporary rise in the total head of the pump turbine caused by the water hammer in the common pipeline as the object of the present invention. As described above, the related art merely discloses a part of the control rules that should be implemented in a single variable speed pumping system. That is, there is no disclosure of a countermeasure against occurrence of backflow in the runner due to water hammer in the shared pipeline as the object of the present invention. [Problems to be Solved by the Invention] The present invention is to solve the above-mentioned problems of the prior art by preventing a backflow from occurring in the runner even when affected by a water hammer from another hydraulic machine sharing a pipeline. With the goal. [Means for Solving the Problems] The variable speed pumping plant of the present invention is connected to one or more branch pipes on the upstream or downstream side to achieve the above object. And a pump whose rotation speed is controlled by the rotation speed control means, and at least one other pump connected to another branch pipe, wherein the rotation speed control means activates another pump, or When the input is suddenly changed, the rotation speed of the pump is controlled to be increased before the head is increased due to the influence of another pump. [Operation] According to the variable speed pumping plant of the present invention, even when the head rises due to water hammer from another pump, the pump is controlled so as to increase the rotation speed of the pump before the head rise. It is possible to prevent a backflow from occurring in advance. A more detailed explanation with examples is as follows. FIG. 6 is a graph in which a Q vs. H relationship graph at each guide vane opening measured at a certain rotation speed is written together.
Under this rotational speed, the optimal adjustment is the dotted envelope. Two lines of FIG. 7 shows the optimal setting curve under the rotational speed N ₁ and N ₂ were determined in the same manner as the envelope of Figure 6. Note that N ₁ >
N _2. That is, it can be considered that the optimum setting curve moves to the upper right when the rotation speed is increased. When the water level difference between the upper pond and the lower pond is the same, the total head H rises as the flow rate Q increases, and this is called a load curve at this water level difference (see FIG. 7). It is elevated total head H under the influence of water hammer in the same guide vane shared conduit so hump characteristics start point H _X increases even under opening raising the obvious as the rotational speed temporary from Figure 7 A drop in hump characteristics can be avoided. Embodiment An embodiment of the present invention will now be described with reference to FIG. Figure 1 is a control circuit diagram according to the present invention (The details about the AC excitation circuit for the power control of not shown since not directly related to the present invention.) And power command P _O from outside the pump at that time Water level difference between upper and lower water tanks, that is, total head H _G
And an adder 18 for comparing the output signal Na from the rotation speed function generator 12 to calculate the appropriate rotation speed Na at that time with the actual rotation speed N, 16 a power control correction signal generator, 7 a power controller, 3 power converter, second electric motor, constituting a control loop consisting of the moment of inertia GD ² in a negative feedback circuit. The GD ² is a block for showing the action of the moment of inertia of the electric motor and the pump, and there is no special device. In addition, the power control correction signal generator 16 includes an integral element to reduce the deviation between Na and N to zero. The correction signal ε, which is the output of the power control correction signal generator 16, is added to the power command P _O and the combined signal P _O +
The actual motor output P _M and ε are compared. Power controller 7, the power converter 3, the power control loop of the generator motor 2 and the actual motor output P _M of the recovery circuit is the power controller 7 is configured in a negative feedback circuit and (P _O + ε) of P _M An integral element is included to reduce the deviation to zero. Load command P _O
The H _G as an input to the guide vane opening function generator 13 for calculating a proper guide vane opening Y _OPT when the comparator 21 for comparing the actual guide vane opening degree Y with the output signal Y _a 9 guide vane control vessel, the actual constitute a control loop consisting of restoration of the guide vane opening Y to the negative feedback circuit, the guide vanes as Y _a and Y deviation of the integration element in the guide vane controller 9 becomes zero control Is done. Thus, N = N _a by the rotation speed control circuit, P _M = P _O + ε by the power control circuit, and Y = Y _a by the full guide vane control circuit. Wherein the deviation of the input P _M to the actual motor and the input P _P where the pump is required is inputted to the moment of inertia of the motor and the pump (GD ^2). By the way, the moment of inertia can be regarded as a kind of integral element. Also as described above 16,7,3,2, the rotation speed control circuit consisting of restoration of the actual N and GD ² is configured in a negative feedback circuit P _M
Is controlled so that the deviation between P and P _P becomes zero. That is, P _M =
P _P, also _P P Y _a = P _O corresponds a since ignoring an error of the function generator to the originally P _O equivalent, i.e. should have been controlled to _P P = P _O. In summary, P _O = P _P = P _M = P _O + ε, and the power correction signal ε is finally set to zero. From the above, the actual input P _M according to the external power command P _O
Can be controlled. FIG. 9 is a graph showing the above description of the embodiment of FIG. Time t ₀ in the driving output command P _O represents the response when is raised stepwise. First motor output P _M rises as graph g with a slight delay. Output N _a of the output Y _a and rotational speed function generator also guide vane opening function generator and a time constant function generator is having unique, each graph b by additional time constant given specially, the c Respond as follows. Response of the actual guide vane opening degree Y with respect to Y _a in the graph b is as shown in d. The presence of a linear portion in the response of Y indicates that the guide blade is limited by the opening speed limitation of the guide blade servomotor (this is given by the stroke control of the guide blade pressure distribution valve, etc.). Rotational speed of the pump N rise ceases upon reaching elevated finally N = N _a as the graph g of the motor output P _M and the graph e of the pump input P _P difference is accelerated by the graph f of. Note that pump input P _P increases as increases the rotational speed N both by the increment added graphs e rise in the guide vane opening degree Y. In the graph f, the movement of the rotation speed N is slow but stable, because the power correction signal transmitter 16 has a sufficient damping action. This can be achieved, for example, by configuring the power correction signal transmitter 16 as a parallel circuit of a proportional element and an integral element and appropriately selecting their gains. The above is a description of a normal case in which a sharp water hammer is not transmitted from another unit sharing a pipeline. However, the operating point correction control means in such a case, which is a point of the present invention, is given as follows. When another unit sharing the upper or downstream pipeline is started in the pumping mode or the input is suddenly increased, a correction signal for increasing the rotational speed of the variable speed pumped power plant by a predetermined value ΔNa in advance and adding a correction signal is added. To the vessel 18. Of course, this ΔNa can be changed according to the guide vane operation amount of the other machine. Further, the ΔNa correction control may be used at the same time when the operation state of the other unit is suddenly changed. Then, when the sudden operation of the other unit is completed and the water hammer in the shared pipeline is stopped, the ΔNa correction signal returns to zero. FIG. 10 summarizes the response of the variable speed pumped storage power plant when the above-described ΔNa correction control is performed. Here on, since other machine that shares the downstream pipe is activated in pumping mode at time t ₁₂ is performed, the time prior to
performs rotation speed correction control of ΔNa at t _11, it is released this in time t _13. In this case, unlike FIG. 8, the motor output command _PO is not moving, so that both Y _OPT and Y are unchanged. FIG. 2 shows a winding type induction motor 2 by the control circuit of FIG.
1 is an example showing a device configuration in the case of using a variable speed motor. The same numbers in the figures indicate the same products. Winding induction machine 2
Is connected to the power system 1 and the secondary side is connected to the power converter 3, and the input of the induction machine 2 is controlled by the phase and voltage control of the AC exciting current by the power converter 3. Actual input P _M is a power detector or actual rotational speed N to the comparator 20 is detected by 6 is detected by the rotational speed detector 5 comparator
Input to 18 respectively. FIG. 9 is a device configuration diagram showing another embodiment of the control circuit of FIG. 1, in which a synchronous machine 10 is used as a variable speed motor, and a power converter 17 is used on the primary side of the system 1 and the synchronous machine 10. It is. A phase detector 11 for matching with a phase command to the power converter is provided. [Effect of the Invention] According to the variable speed pumping plant of the present invention, the rotation speed of its own pump is increased before the head is increased due to the influence of other pumps sharing a pipeline. In addition, even when receiving water hammer from another pump, it is possible to prevent the backflow from occurring in the runner beforehand, and to perform a stable plant operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a control circuit diagram showing one embodiment of the present invention, FIG. 2 is an example in which the present invention is applied to a variable speed pumping plant using a winding type induction motor, and FIG. FIGS. 4 and 5 are explanatory diagrams of the hump characteristic, FIG. 5 is an HQ graph showing the hump characteristic, FIG. 6 is a graph showing the relationship between the guide blade opening degree and the hump characteristic, and FIG. FIG. 8 is a graph showing the relationship.
FIG. 9 is a graph for explaining an embodiment of the present invention, FIG. 9 is an example of a variable speed pumping plant provided with a power converter on the primary side of a generator motor according to an embodiment of the present invention, FIG. FIG. 8 is a graph for explaining the embodiment of the present invention shown in FIG. 1 as in FIG. 8; 25 .. Guide vane.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-175271 (JP, A) JP-A-51-31345 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F04D 15/02 F04D 15/04

Claims (1)

(57) [Claims] A plurality of branch pipes on the upstream side or the downstream side are connected to one of the plurality of branch pipes, and a pump whose rotation speed is controlled by the rotation speed control means is connected to another branch pipe. At least one other pump, wherein the rotation speed control means, when starting the other pump,
Alternatively, when the input of the other pump is suddenly changed, control is performed to increase the rotation speed of the pump before the head is increased due to the influence of the other pump. 2. 3. The variable speed pumping plant according to claim 1, wherein said rotation speed control means cancels the control for increasing the rotation speed of said pump after a predetermined time.