CN111190442A - Newton iteration-based parallel variable-frequency constant-voltage control system operation interval discrimination method - Google Patents

Newton iteration-based parallel variable-frequency constant-voltage control system operation interval discrimination method Download PDF

Info

Publication number
CN111190442A
CN111190442A CN202010004570.3A CN202010004570A CN111190442A CN 111190442 A CN111190442 A CN 111190442A CN 202010004570 A CN202010004570 A CN 202010004570A CN 111190442 A CN111190442 A CN 111190442A
Authority
CN
China
Prior art keywords
frequency
control system
value
pressure
voltage control
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202010004570.3A
Other languages
Chinese (zh)
Other versions
CN111190442B (en
Inventor
彭志辉
冯婧霏
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wenzhou University
Original Assignee
Wenzhou University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wenzhou University filed Critical Wenzhou University
Priority to CN202010004570.3A priority Critical patent/CN111190442B/en
Publication of CN111190442A publication Critical patent/CN111190442A/en
Application granted granted Critical
Publication of CN111190442B publication Critical patent/CN111190442B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D16/00—Control of fluid pressure
    • G05D16/20—Control of fluid pressure characterised by the use of electric means
    • G05D16/2006—Control of fluid pressure characterised by the use of electric means with direct action of electric energy on controlling means
    • G05D16/2013—Control of fluid pressure characterised by the use of electric means with direct action of electric energy on controlling means using throttling means as controlling means

Landscapes

  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Control Of Non-Positive-Displacement Pumps (AREA)

Abstract

The invention relates to a method for judging the running interval of a parallel variable-frequency constant-voltage control system based on Newton iteration, which adopts a sampling period
Figure DDA0002352900290000012
Obtaining pressure values p for intervalsi(k) And an output frequency fi(k) Constructing a mathematical model for online detection of output flow of the parallel variable-frequency constant-voltage control system, acquiring total flow, and obtaining the total flow according to the mathematical model
Figure DDA0002352900290000011
Obtaining the flow Q of the ith pumpiSecondly, constructing a high-efficiency interval, further acquiring the working point of each pump of the parallel variable-frequency constant-voltage control system on a Q-H characteristic curve, and carrying out operation on each pump of the parallel variable-frequency constant-voltage control system on the basis that the working point of the Q-H head characteristic curve of each pump of the parallel variable-frequency constant-voltage control system, the Q-H head characteristic and similar working conditions are acquired in real time to form a high-efficiency operation areaThe interval is accurately and reliably judged, and a basis is provided for the high-efficiency control of the parallel variable-frequency constant-voltage control system.

Description

Newton iteration-based parallel variable-frequency constant-voltage control system operation interval discrimination method
Technical Field
The invention belongs to the field of electromechanical energy-saving control, and particularly relates to a method for judging an operation interval of a parallel variable-frequency constant-voltage control system based on Newton iteration.
Background
The constant pressure control of the fluid has wide application in the fields of petroleum, chemical industry, food, medicine, water supply and drainage, urban water supply and the like, and plays an important role in ensuring the normal operation of industrial and agricultural production and daily life. The pump is a core component of a constant pressure control system, and the operation performance of the pump is directly related to the performance index, especially the energy consumption index, of the whole control system. As a high-energy-consumption general machine, the electric energy consumed by the pump unit accounts for more than 21% of the total national electricity consumption every year, and even accounts for about 60% of the production cost in water supply enterprises. The running efficiency of the pump in the constant-pressure control system is improved by only 1 percent, which brings great benefits to the energy conservation and environmental protection of China, and 30 to 50 percent of the electric energy consumed by the pump can be saved. By adopting the variable frequency control technology, the energy consumption of the pump can be effectively reduced, 282 hundred million kWh of electricity can be saved every year, and the aims of energy conservation and emission reduction are fulfilled. However, the variable-frequency constant-pressure control system needs to ensure that the pump operates in a high-efficiency interval to realize high efficiency and energy conservation. Due to the fact that in the process control fields of petroleum, chemical industry, food, medicine and the like and water supply occasions, the demand of the fluid has randomness and uncertainty in time. The number of pumps which are operated in parallel is required to be increased during the peak period so as to increase the supply amount to meet the requirements of production and living; in the valley, the number of pumps running in parallel is required to be reduced so as to achieve the purpose of energy conservation. Especially during the low valley period, the frequency converter and pump operate at a low frequency due to the small flow. At the moment, the heat loss and the low-frequency vibration of the motor are serious, the energy consumption of the whole variable-frequency constant-voltage control system is increased sharply, and the system efficiency is low. Under the working condition, energy conservation and emission reduction can not be realized, mechanical vibration and serious heating of a motor stator winding are caused by long-term low-frequency operation of the motor, the safety reliability and the service life of the system are reduced, adverse effects are generated on the safety reliability and the production cost of the constant-voltage control system, and even more serious safety accidents are caused.
The high-efficiency operation control of the parallel variable-frequency constant-voltage control system is a common technical problem which needs to be mainly solved for realizing energy conservation, emission reduction, safety and reliability. In order to realize the efficient operation of the variable-frequency constant-pressure control system, the operation interval of the control pump needs to be optimized, and each pump is ensured to be operated in the efficient interval. However, as known from the "optimal control strategy for efficiency of variable-frequency speed-regulating water supply pump station" published in the control theory and application journal by zhanhui et al, there is an efficient operation interval of the pump consisting of a lift characteristic curve and a parabola of similar working condition. When the system runs in the interval, the system can realize high-efficiency running; otherwise, the system operating efficiency and life would be greatly reduced. In order to realize the efficient operation of the pump, the state data of the pump, such as the rotating speed, the flow rate, the delivery lift (or the pressure) and the like, must be optimally controlled, and each pump is ensured to be in an efficient operation interval.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for judging the running interval of a parallel variable-frequency constant-voltage control system based on Newton iteration.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for judging an operation interval of a parallel variable-frequency constant-voltage control system based on Newton iteration comprises the following steps:
step one, a frequency converter i samples a period Ts iObtaining pressure values p for intervalsi(t) simultaneously obtaining the output frequency f of the frequency converter ii(k) And an output frequency array { f) composed of N elements is establishedi(j) Get the output frequency array { f }i(j) Mean value of }
Figure BDA0002352900270000031
And standard deviation SiN is a preset positive integer larger than 1, and k is the current sampling frequency;
step two, the centralized control unit uses the period TcObtaining the average value of all frequency converters for an interval
Figure BDA0002352900270000032
And standard deviation SiAnd obtaining the average frequency adjustment
Figure BDA0002352900270000033
Wherein
Figure BDA0002352900270000034
n is the number of frequency converters;
judging whether the system is in a stable state, if not, adjusting the stability of the system by sending the uniform frequency adjustment quantity to each frequency converter;
step four, when the frequency converter is in a stable state, acquiring a pressure value P of the parallel frequency conversion constant-pressure control system, marking the current moment as t as 0, and applying disturbance delta F to the output frequencies of all frequency converters;
step five, defining t ═ mTsThe estimated value of the flow rate at the time is Qg[m]Where m is 1, 2, …, N, and the estimated value of the hydraulic disturbance amount at this time is defined as Δ pg(m) a limited observation time TdObtaining
Figure BDA0002352900270000035
TdIs a predefined observation time length;
step six, judging whether m is greater than N, if so, then Q is carried out at the momentg[m]For the actual flow rate value of the system, i.e. Q ═ Qg[m](ii) a If not, t is equal to mTcThe pressure value at the moment is recorded as p (m), and the pressure value is obtained
Figure BDA0002352900270000037
Figure BDA0002352900270000038
Is the average value of the pressure collected in a certain time;
step seven, judging
Figure BDA0002352900270000036
If the frequency regulation quantity is not established, the centralized control unit sends the average frequency regulation quantity sigma to the n frequency convertersiWhere i is 1, 2, …, n, Δ p is obtainedg(m)；
Step eight, respectively obtaining the actually measured pressure fluctuation value delta p (m) and the estimated pressure fluctuation value delta p in the mth sampling periodg(m) error e (m) ═ Δ p (m) - Δ pg(m) and error derivative
Figure BDA0002352900270000041
By judging whether | e (m) | < ε are satisfied at the same time1And | e' (m) | < ε2When it is established, Q is determinedg[m]Namely the actual flow value of the parallel variable-frequency constant-pressure water supply system, namely Q is Qg[m]Otherwise, updating the variable m and repeating the step six;
step nine, according to
Figure BDA0002352900270000042
Obtaining the flow Q of the ith pumpi；
Step ten, according to the operation data (Q) of the pumpiP) and Q-H lift characteristics, resulting in a frequency of FiQ-H head characteristic curve of pump
Figure BDA0002352900270000043
The high-efficiency interval of the pump is a rated frequency FNHead characteristic curve HNLowest frequency FminHead characteristic curve HminParabola l under similar working conditionsi1Parabola l under similar working conditionsi2The encircled sector annular area ABCD is used as a high-efficiency area of the pump;
eleventh, judge
Figure BDA0002352900270000044
Upper operating point (Q)iAnd P) whether the frequency is in the high-efficiency interval ABCD, if not, sending the average frequency adjustment quantity sigma to the n frequency converters through the centralized control unitiI is 1, 2, …, n, and the stability of the system is adjusted to be within the high efficiency interval ABCD;
step twelve, if yes, acquiring a Q-H lift characteristic curve
Figure BDA0002352900270000045
Parabolic curve l similar to working conditioni1、li2The intersection points a and b and the corresponding flow rate Qmin、Qmax；
Thirteen, judging min { Q-Qmin，Qmax-Q}≥λ(Qmax-Qmin) Whether or not, if yes, saidIs obviously in the efficient operation interval, wherein lambda is a number between 0 and 0.5, and is determined by the efficient operation interval discrimination performance.
In step seven, through
Figure BDA0002352900270000046
Using the obtained Qg[m]And P, F, Δ F, β, and t ═ mTcTo obtain Δ pg(m), wherein P is the pressure value of the pressure sensor, F is the average value of the output frequency of the frequency converter, Δ F is the frequency disturbance increment, and | Δ F | ═ min { F |, is satisfiedi}，i∈[1，n]And β is a coefficient of mass,
Figure BDA0002352900270000051
k is the spring rate of the spring-loaded energy storage tank, ScThe sectional area of the spring type energy storage tank.
In step three, whether max { | σ is satisfied simultaneously or noti|}≤σrefAnd max { Si}≤SrefTo determine whether the system is in a steady state, where σref，SrefThe positive reference value can be set according to the actual system.
Figure BDA0002352900270000052
The values of (c) include two distribution cases:
1)
Figure BDA0002352900270000053
2)
Figure BDA0002352900270000054
and obtained from two distribution cases
Figure BDA0002352900270000055
Δ p (t) is a pressure fluctuation value caused by Δ F, Δ F is a frequency disturbance increment, and | Δ F | ═ min { F { (F) }is satisfiedi}，i∈[1，n]，ΔQin(t) is the inlet flow fluctuation caused by Δ F, P is the pressure value of the pressure sensor, QThe flow of the inlet and the outlet of the energy storage tank is F, and the average value of the output frequency of the frequency converter is F.
And acquiring the water pressure change amount delta p (t) according to the volume change amount delta v (t) and the spring length change amount delta l (t) of the spring type energy storage tank.
According to
Figure BDA0002352900270000056
And obtaining the water pressure variation amount delta p (t)
Figure BDA0002352900270000057
The invention has the beneficial effects that:
according to the invention, the output flow of each pump of the parallel variable-frequency constant-voltage control system can be detected on line without a flow sensor and an auxiliary circuit, so that the Q-H lift characteristic curve and the working point of each pump are determined, the time and cost required by installation and debugging of the flow sensor and the auxiliary processing circuit are saved, the system structure is simpler, and the system cost is lower;
secondly, on the basis that the working point of the Q-H head characteristic curve of each pump of the parallel variable-frequency constant-voltage control system and the Q-H head characteristic and the similar working condition are obtained in real time to form a high-efficiency operation area, the operation area of each pump of the parallel variable-frequency constant-voltage control system is accurately and reliably identified, and a basis is provided for the high-efficiency control of the parallel variable-frequency constant-voltage control system;
the method for identifying the operation interval of the parallel variable-frequency constant-voltage control system has the characteristics of simplicity, high reliability, strong practicability and the like, and provides reliable guarantee for the safe and efficient operation of the parallel variable-frequency constant-voltage control system.
Drawings
Fig. 1 is a structural diagram of a parallel variable-frequency constant-voltage control system.
Fig. 2 is a schematic diagram of the distribution of the operating frequency of the parallel variable-frequency constant-voltage control system.
Fig. 3 is a graph of the pump efficiency interval distribution.
Fig. 4 is a schematic diagram of the operation interval of the speed regulating pump.
Detailed Description
Assuming that the parallel variable-frequency constant-voltage control system adopts the pumps and the frequency converters with the same model, the invention uses the ith pump (i is more than or equal to 1 and less than or equal to n) and the frequency converter as the exposition objects without losing generality. The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention discloses a Newton iteration-based parallel variable-frequency constant-voltage control system operation interval identification method, which mainly establishes a mathematical model for online flow detection of a parallel variable-frequency constant-voltage control system and provides the parallel variable-frequency constant-voltage control system operation interval identification method according to the established mathematical model and a high-efficiency operation area formed by parabolic enclosure of Q-H lift characteristics and similar working conditions.
a) Output flow mathematical model of parallel variable-frequency constant-voltage control system
The parallel variable frequency constant pressure control system is schematically shown in figure 1 and mainly comprises a liquid source, a centralized control unit, a frequency converter i, a pump i, a check valve i, a gate valve i, a pressure sensor, a spring type energy storage tank and the like, wherein the liquid source is mainly a liquid medium which needs constant pressure control and can be water, oil or other liquid, the centralized control unit mainly has the functions of ① pressure signal acquisition, ② communication with the frequency converter to realize the flow rate control of the constant pressure control system and the optimal dispatching control of the pump, ③ human-computer interface function to obtain the input of parameters and display of the operation state, the frequency converter mainly has the functions of ① uploading the current operation state including the starting/stopping state, the operation frequency value and other voltage and current information, ② receives the pressure value and the frequency regulating quantity sent by the centralized control unit to adjust the rotating speed of the pump to realize the constant pressure control and flow rate control functions, the pump i conveys the liquid in the liquid source to a pipeline through high-speed rotation of an impeller blade, the check valve i mainly has the function of preventing backflow, the gate valve i is used for realizing the connection and disconnection of the pump and the pressure sensor is used for detecting the pressure storage pipe network, and stabilizing the pressure.
The variables are described as follows: f. ofi(t) is the output frequency of the frequency converter i; qi(t) is the outlet flow rate of pump i, i ═ 1, 2, …, n; qin(t) is the inlet flow of the spring type energy storage tank; qout(t) the outlet flow of the spring type energy storage tank is also the output flow; p (t) is the pressure value of the pipe network; the spring stiffness of the spring type energy storage tank is K; the sectional area of the spring type energy storage tank is Sc(ii) a t is a time variable.
As known from knowledge of centrifugal pumps and alternating current motors, the output power of the ith pump is in the following relation:
Figure BDA0002352900270000081
wherein: qi(t)×pi(t) actual output Power, ηiTo be efficient, siFor slip, R1，R2，X1σ，X2σ，m1，
Figure BDA0002352900270000082
As a parameter inherent to the AC motor, fiAnd (t) is the output frequency of the ith frequency converter.
Consider that every pump export the model shape of pipeline and valve to energy storage tank water inlet department, there is less difference just to the distance between the energy storage tank water inlet to constant voltage control system's output lift is greater than pump far away and pumps the pipe resistance to energy storage tank water inlet department, so can obtain:
pi(t)＝pj(t)≈p(t) (2)
wherein: i, j ≠ j {1, 2, 3, …, n }, i ≠ j; p (t) is the pressure sensor pressure value;
since the parallel constant voltage control system adopts the uniform frequency control, the control method can be applied to the control of the parallel constant voltage control system
Figure BDA0002352900270000086
Comprises the following steps:
|fi(t)-F(t)|≤σ(t) (3)
wherein: f (t) is the frequency average value
Figure BDA0002352900270000083
And sigma (t) is the average frequency performance index.
Because the frequency converter and the centralized control unit use a control chip with excellent performance and an average frequency control algorithm, the situation that sigma (t) is very small can be ensured. Considering that the AC motor and the frequency converter have the same type and adopt frequency conversion control, the AC motor and the frequency converter have the same mechanical characteristic curve and corresponding slip ratio siAnd efficiency ηiApproximately equal, i.e.:
Figure BDA0002352900270000084
order:
Figure BDA0002352900270000085
then the simultaneous (4) yields:
Ci＝Cj＝C (5)
wherein:
Figure BDA0002352900270000091
therefore, for
Figure BDA0002352900270000097
Comprises the following steps:
Qi(t)×p(t)＝C×fi(t)2(6)
and because of
Figure BDA0002352900270000092
Therefore, the method comprises the following steps:
Figure BDA0002352900270000093
the parameters of the parallel variable-frequency constant-voltage control system in a relatively steady state are defined as follows: the pressure value of the pressure sensor is P, the flow of the inlet and the outlet of the energy storage tank is Q, the average value of the output frequency of the frequency converter is F,the performance parameter of the average frequency is delta, and the output frequency of the frequency converter i is FiAll quantities mentioned above are in international units. Defining the moment when t is 0 as the last moment of the parallel variable-frequency constant-voltage control system relative to the steady state, namely:
Figure BDA0002352900270000094
then there are:
|Fi-F|≤δ (9)
Figure BDA0002352900270000095
wherein:
Figure BDA0002352900270000096
suppose to be at (0, T)d]The frequency converter output frequency is regulated to be by the parallel connection frequency conversion constant voltage control system integrated controller in time: f. ofi(t)＝Fi+ Δ F, Δ F is the frequency perturbation increment and satisfies | Δ F | ═ min { F |i}，i∈[1，n]；TdThe time value is a predefined observation time length and is a time value greater than 0, and the time value is artificially determined according to different performance indexes of the constant pressure control system; the pressure sensor value is P (t) ═ P + Δ P (t), and Δ P (t) is the pressure fluctuation value caused by Δ F; inlet flow of the energy storage tank is Qin(t)＝Q+ΔQin(t)，ΔQin(t) is the inlet flow fluctuation caused by Δ F; the outlet flow of the energy storage tank is Qout(t)＝Q+ΔQout(t)，ΔQout(t) is the outlet flow fluctuation value caused by delta F;
in T ∈ (0, T)d]Is mixing Q within(t)＝Q+ΔQin(t)，fi(t)＝FiThe expression (7) is substituted with + Δ F and P (t) ═ P + Δ P (t):
Figure BDA0002352900270000101
unfolding (11) and finishing to obtain:
Figure BDA0002352900270000102
combining (10) and (12), and finishing to obtain:
Figure BDA0002352900270000103
because of the existence of a large inertia damping link of the energy storage tank, and | delta F | ═ min { F |)i}，i∈[1，n]Then at T e (0, T)d]The pressure variation delta p (t) caused by the flow change of the inlet and the outlet of the energy storage tank in a short time is very small, and the requirements are as follows:
|Δp(t)|＝P (14)
since | Δ F | ═ min { F |)iP, so equation (13) can be approximated as:
Figure BDA0002352900270000104
dividing (15) by (10) yields:
Figure BDA0002352900270000111
will be provided with
Figure BDA0002352900270000112
Substitution (16) can give:
Figure BDA0002352900270000113
at present
Figure BDA0002352900270000114
Figure BDA0002352900270000114
① consider an extreme distribution, as shown in FIG. 2(a), with:
Figure BDA0002352900270000115
wherein: sigmau＝F-Fu，σj＝Fj-F，σu＞0，σ j0 of (A); therefore, the method comprises the following steps:
Figure BDA0002352900270000116
and (3) unfolding and arranging the materials to obtain:
Figure BDA0002352900270000117
the simultaneous (18), (20) can obtain:
Figure BDA0002352900270000118
② consider the other extreme distribution case, namely FiEven distribution, as shown in fig. 2(b), there are:
Figure BDA0002352900270000119
wherein: i.e. ik，in-k+1＝{1，2，…，n}；ik≠in-k+1；
Figure BDA00023529002700001211
Then:
Figure BDA0002352900270000121
wherein:
Figure BDA0002352900270000122
finishing (23) to obtain:
Figure BDA0002352900270000123
therefore:
Figure BDA0002352900270000124
wherein:
Figure BDA0002352900270000125
from the geometrical knowledge, F for any other distributioniWhich is
Figure BDA0002352900270000126
Values lie between the two extreme distributions, so there are:
Figure BDA0002352900270000127
considering that the unbalance degree of the average frequency control system with the most common performance is within 10 percent, namely delta is less than or equal to 0.1F, the delta is2＜＜F2，
Figure BDA0002352900270000128
Thus, there are:
Figure BDA0002352900270000129
the simultaneous formulas (17) and (27) can be obtained:
Figure BDA00023529002700001210
since at T ∈ (0, T)d]With | Δ P (t) | ═ P, i.e. the pipe network pressure remains almost constant, and the outlet flow of the accumulator tank changes by an amount Δ Q without changing the pipe resistance characteristicsout(t) ≈ 0, i.e. Qout(t) ≈ Q. In T ∈ (0, T)d]The volume change of the liquid in the energy storage tank is as follows:
Figure BDA0002352900270000131
therefore, T ∈ (0, T)d]The length variation quantity delta l (t) of the energy storage tank spring is as follows:
Figure BDA0002352900270000132
therefore, T ∈ (0, T)d]The water pressure change quantity delta p (t) of the energy storage tank is as follows:
Figure BDA0002352900270000133
combining (28) and (31) and finishing to obtain:
Figure BDA0002352900270000134
order:
Figure BDA0002352900270000135
then there are: y' (t) ═ Δ Qin(t) and y (0) ═ 0, and formula (32) can be collated:
Figure BDA0002352900270000137
equations (28) and (33) are combined and solved to obtain:
Figure BDA0002352900270000138
coefficient of order
Figure BDA0002352900270000139
Then:
Figure BDA00023529002700001310
since the parameters Δ P (T), P, Δ F, F, β, and T are all observable and known quantities, by taking the value at T ∈ (0, T ∈ (T))d]The value of the pressure variation delta p (t) can be used for measuring the output flow value Q of the parallel variable-frequency constant-pressure control system in a steady state on line.
Meanwhile, from a similar theorem of pumps, it can be known that: when the pumps with similar geometry operate under similar working conditions, the flow Q and the operating speed n of the pumps meet the following conditions:
Figure BDA0002352900270000141
the centrifugal pump and the frequency converter of the parallel connection frequency conversion constant voltage control system have the same model, are in the same pipe network and the centralized control unit performs frequency-equalizing control on the running frequency converter, so that the ith centrifugal pump and the jth centrifugal pump meet the similar law, so that the frequency-equalizing control system has the following functions:
Figure BDA0002352900270000142
wherein: n isiThe rotating speed of the ith centrifugal pump is set; n isjThe rotating speed of the jth centrifugal pump;
the rotating speed n of the centrifugal pump meets the following conditions:
Figure BDA0002352900270000143
wherein: f is the output frequency of the frequency converter; s is the slip ratio; p is the pole pair number of the centrifugal pump; the simultaneous (4), (37) and (38) can obtain:
Figure BDA0002352900270000144
therefore, the method comprises the following steps:
Figure BDA0002352900270000145
wherein: i ═ 1, 2, … n }. Will be provided with
Figure BDA0002352900270000146
Substitution (40) has:
Figure BDA0002352900270000147
b) parallel variable frequency constant voltage control system operation interval estimation
Each of the parallel variable-frequency constant-voltage control systems can be obtained according to a formula (41)Flow Q of the pump at any relatively steady-state timei. Meanwhile, the output lift H of the parallel variable-frequency constant-voltage control system and the operating frequency F of each pumpi. The value of the voltage reference value can be obtained through a pressure sensor and the output frequency of a reading frequency converter, and then the working point of each pump of the parallel variable-frequency constant-voltage control system on a Q-H characteristic curve is obtained.
FIG. 3 is a graph showing the distribution of the high-efficiency interval of the pump at a rated frequency FNHead characteristic curve HNLowest frequency FminHead characteristic curve HminParabola l under similar working conditionsi1Parabola l under similar working conditionsi2A fan-shaped annular area ABCD. If the pump is in the region ABCD at the operating point of the Q-H characteristic curve, then efficient operation is in progress; otherwise, the system is in a non-efficient operation state.
Because the parallel variable-frequency constant-voltage control system adopts the variable-frequency speed regulation to realize the pressure control mode, the lift characteristic curve of the pump has the translation characteristic under the condition of different operating frequencies. The operation section distribution is described in detail below.
(1) The lift P is unchanged, the valve opening is changed:
suppose that the ith pump operates at a frequency of
Figure BDA0002352900270000151
Its lift characteristic curve is H1The lift value of the operating point 1 is P, and the flow rate is Q1As can be seen from FIG. 4(a), the operation point 1 is in the high-efficiency operation interval ABCD, when the flow rate is reduced due to the decrease of the valve opening degree of ①, the operation frequency of the parallel variable-frequency constant-voltage control system is necessarily reduced under the condition of maintaining the output lift P unchanged, and the operation frequency is Fi 2The lift characteristic curve is switched to H2The lift value of the operating point 2 is P and the flow rate is Q2As can be seen from FIG. 3, the operation point 2 is not in the high-efficiency area ABCD, the efficiency is lower as the operation point deviates from the high-efficiency operation interval, when the flow is increased due to the increase of the valve opening degree of ②, the operation frequency of the parallel variable-frequency constant-pressure control system is inevitably increased under the condition of maintaining the output lift P unchanged, and at the moment, the operation is carried outFrequency of Fi 3The lift characteristic curve is switched to H3The lift value of the operating point 3 is P and the flow rate is Q3. As can be seen from fig. 3, the operating point 3 is not located in the high-efficiency region ABCD, and the efficiency decreases as it deviates further from the high-efficiency operating interval.
(2) The lift P changes, the valve opening is unchanged:
assume that the current pump is operating at a frequency Fi 1The pump head characteristic curve is H1The lift corresponding to the running point 1 is P1At a flow rate of Q1As can be seen from FIG. 4(b), the operating point 1 is in the high-efficiency operating region ABCD, and the following two cases are analyzed, ① setting the head P1Decrease to P2In the process, the operation frequency of the parallel variable-frequency constant-pressure control system is inevitably reduced under the condition that the opening degree of the valve is unchanged, and the operation frequency is Fi 2The lift characteristic curve is switched to H2The lift value of the operating point 2 is P2At a flow rate of Q2As can be seen from FIG. 4(b), the operating point 2 is not located in the high efficiency region ABCD, ② sets the head P1Increase to P3In the process, the operation frequency of the parallel variable-frequency constant-pressure control system is inevitably increased under the condition that the opening degree of the valve is unchanged, and the operation frequency is Fi 3The lift characteristic curve is switched to H3The lift value of the operating point 3 is P3At a flow rate of Q3. As can be seen from fig. 4(b), the operating point 3 is not located in the high efficiency area ABCD;
through the analysis, the operation interval of the parallel variable-frequency constant-voltage control system pump is not always in the high-efficiency interval operation, and changes along with the changes of the output lift, the output flow and the system pipe resistance.
The invention provides a method for judging an operation interval of a parallel variable-frequency constant-voltage control system based on Newton iteration, which comprises the following steps of:
(1) frequency converter i with sampling period Ts iFor sampling pressure values at intervals, the first sampling value isMark pi(1) (ii) a The current sampling frequency is k, and k is made to be 1; wherein: i ═ {1, 2, …, n };
(2) the frequency converter i executes a frequency conversion constant voltage control algorithm and an average frequency control algorithm to obtain an output frequency fi(k) And establishing an output frequency array { f) of the frequency converter i consisting of N elementsi(j) Get { f }i(j) Mean value of }
Figure BDA0002352900270000172
And standard deviation of
Figure BDA0002352900270000173
Wherein: j is { k-N +1, k-N +2,. k }, N is a preset positive integer greater than 1, and k is the current sampling frequency; f. ofi(j)|j＜＝0＝0；
(3) The central control unit is controlled with a period TcFor communication with frequency converters at intervals, all frequency converters being acquired
Figure BDA00023529002700001711
And Si. Calculating the average frequency adjustment
Figure BDA0002352900270000174
Wherein:
Figure BDA0002352900270000175
(4) judging whether the parallel variable-frequency constant-voltage control system is in a stable state, wherein the stable state is defined as: judging whether max { | sigma is satisfied at the same timei|}≤σrefAnd max { Si}≤Sref. Wherein: sigmaref， SrefThe positive reference value can be set according to the actual system, and can be 0.1 or 0.2, for example. If so, the parallel variable-frequency constant-voltage control system is considered to be in a stable state, and the step (5) is carried out; otherwise, the constant pressure control system is in an unstable state, and the step (17) is carried out;
(5) acquiring a pressure value P of a parallel variable-frequency constant-pressure control system;
(6) with the time scale t being 0,and applying a fixed arbitrary disturbance deltaF to all frequency converter output frequencies via the communication bus, i.e.
Figure BDA0002352900270000176
(7) Definition of Qg[m]Is t ═ mTs(m-1, 2, …, N) time flow estimate, defining Δ pg(m) is the corresponding water disturbance variable, TdIn order to observe the defined time, the time is limited,
Figure BDA0002352900270000177
order: m is 1; e (0) ═ 0; e' (0) ═ 0; setting the initial value of the flow estimation to
Figure BDA0002352900270000178
Wherein
Figure BDA0002352900270000179
An initial value of a flow estimation value which is set arbitrarily; in order not to lose generality,
Figure BDA00023529002700001710
the value is large.
(8) Judging whether m is greater than N, if so, turning to the step (11); otherwise, get t ═ mTcThe pressure value at the moment is denoted as p (m); and calculate
Figure BDA0002352900270000181
(9) Judgment of
Figure BDA0002352900270000182
Whether the result is true (α is any set value, but 0.1, 0.05 or other numbers, and is determined by the pressure performance index requirement of the constant pressure water supply system). The basis for satisfying the expression is that the system pressure can not be caused to fluctuate dramatically when the frequency change delta F operation is carried out, otherwise, the precondition that the system pressure is lost exists is removed.A step (17) is carried out if the result is not true, otherwise, an estimated value Q is carried outg[m]And P, F, Δ F, β and t ═ mTcSubstituting into a formula:
Figure BDA0002352900270000183
solving to obtain delta pg(m)。
(10) Respectively obtaining e (m) ═ Δ p (m) — Δ pg(m) and
Figure BDA0002352900270000184
wherein: e (m), e' (m) respectively represents the measured pressure fluctuation value delta p (m) and the estimated pressure fluctuation value delta p in the mth sampling periodg(m) error and error derivative.
Judging whether | e (m) | < epsilon1And | e' (m) | < ε2(wherein:. epsilon.1，ε2Respectively, setting a very small positive number, and performing setting according to an actual system, such as setting to 0.1 or 0.2, and the like), and if so, entering step (11);
otherwise, updating the variable and the estimated value;
making m equal to m + 1; qg[m]＝Qg[m-1]-e′[m-1]e[m-1]And returning to the step (8).
(11)Qg[m]Namely the actual flow value of the parallel variable-frequency constant-pressure water supply system, namely Q is Qg[m]。
(12) Q is added,
Figure BDA0002352900270000187
Substituting n and F into the formula:
Figure BDA0002352900270000188
detecting the flow Q of the ith pumpi；
(13) According to pump operating data (Q)iP) and Q-H head characteristics have a translational characteristic giving a frequency FiThe Q-H head characteristic curve of the pump is recorded as
Figure BDA0002352900270000191
(14) Judgment of
Figure BDA0002352900270000192
Go up fortuneRow point (Q)iP) is within the high efficiency area ABCD. If yes, entering the step (15); otherwise, the operation is not in the efficient operation interval, and the step (17) is entered.
(15) Calculating a curve
Figure BDA0002352900270000193
Parabolic curve l similar to working conditioni1、li2Is marked as points a, b and the corresponding flow rate Qmin、Qmax。
(16) Determine min { Q-Qmin，Qmax-Q}≥λ(Qmax-Qmin) Whether or not (wherein: λ is a number between 0 and 0.5, determined by the efficient operation interval discrimination performance). If yes, indicating that the system is in the high-efficiency operation interval, and entering the step (17); otherwise, the operation is not in the efficient operation interval, and the step (17) is entered.
(17) The centralized control unit sends the frequency regulating quantity sigma of the uniform frequency control algorithm to the n frequency converters through the communication busi(i＝1，2，…，n)；
(18) Let k be k + 1; carrying out next sampling, and marking the sampling value of the output pressure as pi(k) (ii) a And (4) returning to the step (2).
The examples should not be construed as limiting the present invention, but any modifications made based on the spirit of the present invention should be within the scope of protection of the present invention.

Claims (6)

1. A method for judging an operation interval of a parallel variable-frequency constant-voltage control system based on Newton iteration is characterized by comprising the following steps of: which comprises the following steps:
step one, a frequency converter i samples according to a sampling period
Figure FDA0002352900260000018
Obtaining pressure values p for intervalsi(t) simultaneously obtaining the output frequency f of the frequency converter ii(k) And an output frequency array { f) composed of N elements is establishedi(j) Get the output frequency array { f }i(j) Mean value of }
Figure FDA0002352900260000011
And standard deviation SiN is a preset positive integer larger than 1, and k is the current sampling frequency;
step two, the centralized control unit uses the period TcObtaining the average value of all frequency converters for an interval
Figure FDA0002352900260000012
And standard deviation SiAnd obtaining the average frequency adjustment
Figure FDA0002352900260000013
Wherein
Figure FDA0002352900260000014
n is the number of frequency converters;
judging whether the system is in a stable state, if not, adjusting the stability of the system by sending the uniform frequency adjustment quantity to each frequency converter;
step four, when the frequency converter is in a stable state, acquiring a pressure value P of the parallel frequency conversion constant-pressure control system, marking the current moment as t as 0, and applying disturbance delta F to the output frequencies of all frequency converters;
step five, defining t ═ mTsThe estimated value of the flow rate at the time is Qg[m]Where m is 1, 2, …, N, and the estimated value of the hydraulic disturbance amount at this time is defined as Δ pg(m) a limited observation time TdObtaining
Figure FDA0002352900260000015
TdIs a predefined observation time length;
step six, judging whether m is greater than N, if so, then Q is carried out at the momentg[m]For the actual flow rate value of the system, i.e. Q ═ Qg[m](ii) a If not, t is equal to mTcThe pressure value at the moment is recorded as p (m), and the pressure value is obtained
Figure FDA0002352900260000016
Figure FDA0002352900260000017
Is the average value of the pressure collected in a certain time;
step seven, judging
Figure FDA0002352900260000021
If the frequency regulation quantity is not established, the centralized control unit sends the average frequency regulation quantity sigma to the n frequency convertersiI is 1, 2, …, n, and in the case where this is true, the estimated pressure fluctuation value Δ p is acquiredg(m)；
Step eight, respectively obtaining the actually measured pressure fluctuation value delta p (m) and the estimated pressure fluctuation value delta p in the mth sampling periodg(m) error e (m) ═ Δ p (m) - Δ pg(m) and error derivative
Figure FDA0002352900260000022
By judging whether | e (m) | < ε are satisfied at the same time1And | e' (m) | < ε2When it is established, Q is determinedg[m]Namely the actual flow value of the parallel variable-frequency constant-pressure water supply system, namely Q is Qg[m]Otherwise, updating the variable m and repeating the step six;
step nine, according to
Figure FDA0002352900260000023
Obtaining the flow Q of the ith pumpiQ is the flow rate of an inlet and an outlet of the energy storage tank, F is the average value of the output frequency of the frequency converter, and n is the number of the pumps;
step ten, according to the operation data (Q) of the pumpiP) and Q-H lift characteristics, resulting in a frequency of FiQ-H head characteristic curve of pump
Figure FDA0002352900260000024
The high-efficiency interval of the pump is a rated frequency FNHead characteristic curve HNLowest frequency FminHead characteristic curve HminParabola l under similar working conditionsi1Parabola l under similar working conditionsi2The encircled sector annular area ABCD is used as a high-efficiency area of the pump;
eleventh, judge
Figure FDA0002352900260000025
Upper operating point (Q)iAnd P) whether the frequency is in the high-efficiency interval ABCD, if not, sending the average frequency adjustment quantity sigma to the n frequency converters through the centralized control unitiI is 1, 2, …, n, and the stability of the system is adjusted to be within the high efficiency interval ABCD;
step twelve, if yes, acquiring a Q-H lift characteristic curve
Figure FDA0002352900260000026
Parabolic curve l similar to working conditioni1、li2The intersection points a and b and the corresponding flow rate Qmin、Qmax；
Thirteen, judging min { Q-Qmin，Qmax-Q}≥λ(Qmax-Qmin) And if yes, indicating that the system is in a high-efficiency operation interval, wherein lambda is a number between 0 and 0.5, and is determined by the high-efficiency operation interval judging performance.
2. The method for distinguishing the operation interval of the parallel variable-frequency constant-voltage control system based on Newton iteration according to claim 1, wherein: in step seven, through
Figure FDA0002352900260000031
Using the obtained Qg[m]And P, F, Δ F, β, and t ═ mTcTo obtain Δ pg(m), wherein P is the pressure value of the pressure sensor, F is the average value of the output frequency of the frequency converter, Δ F is the frequency disturbance increment, and | Δ F | ═ min { F |, is satisfiedi}，i∈[1，n]And β is a coefficient of mass,
Figure FDA0002352900260000032
k is the spring rate of the spring-loaded energy storage tank, ScIs a spring type accumulatorCross-sectional area of the energy tank.
3. The method for distinguishing the operation interval of the parallel variable-frequency constant-voltage control system based on Newton iteration according to claim 1, wherein: in step three, whether max { | σ is satisfied simultaneously or noti|}≤σrefAnd max { Si}≤SrefTo determine whether the system is in a steady state, where σref，SrefThe positive reference value can be set according to the actual system.
4. The method for distinguishing the operation interval of the parallel variable-frequency constant-voltage control system based on Newton iteration according to claim 1, wherein:
Figure FDA0002352900260000033
the values of (c) include two distribution cases:
1)
Figure FDA0002352900260000034
2)
Figure FDA0002352900260000035
and obtained from two distribution cases
Figure FDA0002352900260000036
Δ p (t) is a pressure fluctuation value caused by Δ F, Δ F is a frequency disturbance increment, and | Δ F | ═ min { Fi }, i ∈ [1, n }, and]，ΔQinand (t) is an inlet flow fluctuation value caused by delta F, P is a pressure value of the pressure sensor, Q is the inlet and outlet flow of the energy storage tank, and F is an average value of the output frequency of the frequency converter.
5. The method for distinguishing the operation interval of the parallel variable-frequency constant-voltage control system based on Newton iteration according to claim 4, wherein: and acquiring the water pressure change amount delta p (t) according to the volume change amount delta v (t) and the spring length change amount delta l (t) of the spring type energy storage tank.
6. The method for distinguishing the operation interval of the parallel variable-frequency constant-voltage control system based on Newton iteration according to claim 5, wherein: according to
Figure FDA0002352900260000041
And obtaining the water pressure variation amount delta p (t)
Figure FDA0002352900260000042
CN202010004570.3A 2020-01-02 2020-01-02 Method for discriminating running interval of parallel variable frequency constant voltage control system Active CN111190442B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202010004570.3A CN111190442B (en) 2020-01-02 2020-01-02 Method for discriminating running interval of parallel variable frequency constant voltage control system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202010004570.3A CN111190442B (en) 2020-01-02 2020-01-02 Method for discriminating running interval of parallel variable frequency constant voltage control system

Publications (2)

Publication Number Publication Date
CN111190442A true CN111190442A (en) 2020-05-22
CN111190442B CN111190442B (en) 2023-06-09

Family

ID=70708032

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202010004570.3A Active CN111190442B (en) 2020-01-02 2020-01-02 Method for discriminating running interval of parallel variable frequency constant voltage control system

Country Status (1)

Country Link
CN (1) CN111190442B (en)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008014230A (en) * 2006-07-06 2008-01-24 Sayama Seisakusho:Kk Method and system for flow rate estimation of parallel pump provided in water supply system
JP2010019222A (en) * 2008-07-14 2010-01-28 Sayama Seisakusho:Kk Pressure control method and pressure control system of pump
JP2010216288A (en) * 2009-03-13 2010-09-30 Sayama Seisakusho:Kk Parallel-off control method for parallel pump and parallel-off control system for parallel pump
CN108287571A (en) * 2018-01-26 2018-07-17 温州大学 A kind of flow control system pump operation interval judgement method
CN108415466A (en) * 2018-01-26 2018-08-17 温州大学激光与光电智能制造研究院 A kind of flow control system pump operation method of interval estimation
CN108490988A (en) * 2018-01-26 2018-09-04 温州大学激光与光电智能制造研究院 A kind of flow control system pump operation section method of discrimination

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008014230A (en) * 2006-07-06 2008-01-24 Sayama Seisakusho:Kk Method and system for flow rate estimation of parallel pump provided in water supply system
JP2010019222A (en) * 2008-07-14 2010-01-28 Sayama Seisakusho:Kk Pressure control method and pressure control system of pump
JP2010216288A (en) * 2009-03-13 2010-09-30 Sayama Seisakusho:Kk Parallel-off control method for parallel pump and parallel-off control system for parallel pump
CN108287571A (en) * 2018-01-26 2018-07-17 温州大学 A kind of flow control system pump operation interval judgement method
CN108415466A (en) * 2018-01-26 2018-08-17 温州大学激光与光电智能制造研究院 A kind of flow control system pump operation method of interval estimation
CN108490988A (en) * 2018-01-26 2018-09-04 温州大学激光与光电智能制造研究院 A kind of flow control system pump operation section method of discrimination

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
干浙民: "恒压变流量供水系统中值得研讨的几个问题" *
樊建军;梁志君;董毅;崔艳堂;: "水泵选型与运行模式对变频调速供水系统能耗的影响" *

Also Published As

Publication number Publication date
CN111190442B (en) 2023-06-09

Similar Documents

Publication Publication Date Title
CN110953169B (en) Control method of parallel variable-frequency constant-voltage control system
CN110954172B (en) Flow detection method for parallel variable-frequency constant-pressure water supply system
CN108287571B (en) Method for judging running interval of flow control system pump
CN103452824B (en) Based on the energy saving in fans and pumps system of the minimum power algorithm of flow-power curve
CN104141603B (en) There is the control system of water pump of energy-conserving action
CN109185972B (en) Heat station circulating pump optimization adjusting method
CN103452829B (en) A kind of frequency-conversion water supply system operational efficiency online test method
CN103485386B (en) Variable frequency constant-pressure water supply system control method based on gray correlation method
CN201292954Y (en) Water pump and/or blower fan highly effective energy-conserving control system
CN111043047B (en) Method for distinguishing running section of parallel variable-frequency constant-voltage control system
CN101994704B (en) Chemical process intelligent pump and control method thereof
CN103488082B (en) A kind of high-efficiency frequency conversion constant pressure water supply system control method based on inverse estimation method
CN111190442A (en) Newton iteration-based parallel variable-frequency constant-voltage control system operation interval discrimination method
CN201771737U (en) Electricity economization controller capable of leading water pump to run at optimum revolution
CN111190443B (en) Control method of parallel variable frequency constant voltage control system based on Newton iteration
CN111219600B (en) Flow detection method of parallel variable-frequency constant-pressure water supply system based on Newton iteration
CN206376832U (en) Energy-saving control system of beam-pumping unit
CN103487186B (en) Variable frequency water supply system operating efficiency on-line detection method based on grey correlation method
CN201637332U (en) Intelligent controller for energy-saving operation of cooling tower
CN204757124U (en) Unsteady flow volume and central heating system who divides family measurement
CN103487099B (en) A kind of low discharge online test method based on parameter reverse method
CN203808157U (en) Energy-saving water supply system capable of realizing pressure change with flow
CN205718643U (en) The heat-exchange unit of pressure fixing system
CN103471662B (en) Small flow online detecting method based on Newton method
CN204987465U (en) Integrated air can water heater

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant