CN205212429U - Optimize control system of DC distribution net trend - Google Patents

Abstract

The utility model discloses an optimize control system of DC distribution net trend, this system include a central processing unit, a plurality of load side and equivalent measurement and control terminal, two current conversion stations station accuse system, and all measurement and control terminal between, between a central processing unit and each measurement and control terminal and a central processing unit and two current conversion stations communication network between the accuse system of standing, measurement and control terminal and load side one -to -one for gather corresponding load side's power, two current conversion stations station accuse systems in one for deciding direct current voltage control current conversion station, another is deciding the dc power current conversion station. This system can guarantee that whole straight each terminal voltage of flow net twine is not out -of -limit for the active power distribution is more reasonable, obtains wideer direct current voltage control scope and lower straight flow net twine loss simultaneously.

Description

A kind of control system optimizing DC distribution net trend

Technical field

The utility model relates to a kind of control system optimizing DC distribution net trend, particularly relates to a kind of control system of the DC distribution net trend for optimizing band two power ends.

Background technology

Along with the high speed development of device for high-power power electronic, high-voltage commutation technology, high voltage dc transmission technology have also been obtained constantly perfect.DC distribution net is intelligence, a stable alternating current-direct current mixing Wide Area Network with advanced energy management system.Compared with AC distribution net, DC distribution net also exists following obvious advantage: when insulation level is identical, and the through-put power of DC distribution net is about 1.5 times of AC distribution net; DC distribution net can facilitate the access of various distributed power source and electric automobile charging station; Being different from AC distribution net, there is not the reactive loss of eddy current loss and circuit in DC distribution net, and the loss of DC distribution net is only 15% ~ 50% of AC network; Direct current system does not have the problems such as frequency departure, imbalance of three-phase voltage and reactive power compensation in theory, therefore, it is possible to effectively avoid the problems such as voltage fluctuation and flicker, frequency shift (FS), harmonic pollution, effectively can improve the quality of power supply, improves electric network reliability.

The major control object of direct-flow distribution system maintains stablizing of busbar voltage, has the control strategy that a kind of voltage droop controls at present.It refers to the control mode that all converters possessing power adjustments ability all run on direct voltage.Under this control model, voltage-regulation and power division, by multiple current conversion station shared, according to current conversion station P-V characteristic curve, determine that this node power distributes and voltage regulation capability and its control characteristic is non-linear (hyperbola).When converter terminal voltage is fallen, it is exerted oneself to increase and stablizes in order to ME for maintenance, but can return to normal condition then must judge according to its characteristic curve.Therefore the weak point of this kind of control mode is to there is voltage static difference, and with the expansion of system scale, its stable operation interval will narrow, and power division flexibility is short of to some extent.In addition, when system overhaul or fault cause that a certain current conversion station is out of service, wind power plant input power fluctuation etc. time, tradition droop control strategy still carries out power division according to original coefficient, cannot regulate according to the actual conditions of system cloud gray model, make that current conversion station capacity utilization is lower, DC bus-bar voltage is second-rate, even occur that current conversion station power transfinites obviously, such control strategy well can not be applicable to DC distribution net stability being had to high request.

Summary of the invention

The purpose of this utility model is for the deficiencies in the prior art, a kind of control system optimizing DC distribution net trend is provided, the each terminal voltage of whole DC network is not out-of-limit to adopt this system to ensure, active power is distributed more reasonable, obtain wider DC voltage control scope and lower DC network loss simultaneously.

The control system of optimization DC distribution net trend of the present utility model, it is characterized in that, comprise the communication network between the detection and control terminal of a CPU, some load sides and equivalent, two Converter Station Ore-controlling Role and all detection and control terminals, between CPU and each detection and control terminal and between CPU and two Converter Station Ore-controlling Role; Described detection and control terminal and load side one_to_one corresponding, for gathering the power of corresponding load side, in two described Converter Station Ore-controlling Role, one is constant DC voltage control current conversion station, and another is for determine direct current power current conversion station.

This system is adopted to be optimized the control method of DC distribution net trend, the method is n section by determining direct current power end power divider, magnitude of voltage corresponding in minimal network loss situation and performance number is asked for after carrying out Load flow calculation successively, have employed the method that performance number and magnitude of voltage separately solve, solution procedure simplifies and computational speed is very fast, can choose the value of the total sector number n of power divider according to accuracy requirement flexibly.Active power is distributed more reasonable, obtain wider DC voltage control scope and lower network loss simultaneously.

Specifically: be n section by the power divider of determining direct current power end, DC network loss 0≤k≤n, the k ∈ N of a kth section is solved according to the following steps:

(1) obtain power distribution network network parameter and node power and inject information, comprising: bus numbering, title, load are gained merit, the branch road of transmission line number, headend node and endpoint node is numbered, series resistance;

(2) determining direct current pressure side initial voltage value is the rated voltage U=U of direct current system _n, the initial value of k is 0;

(3) determining direct current power end initial power is wherein P _nfor determining direct current power section rated power, n is the section sum of the power divider of determining direct current power end, k in this time calculating get the corresponding sequence number of section;

(4) carry out Load flow calculation, set up DC power flow equation and iterative, obtain each node voltage value and each branch current value;

(5) check each node voltage, be divided into following three kinds of situations to consider:

Situation 1, there is node voltage lower than voltage stabilization lower limit U _min, then the voltage U increase 1%U of direct current pressure side is determined in order _nif now there is node voltage higher than voltage stabilization higher limit U _max, then DC network loss is made wherein P _loadfor load side gross power, enter (6); If now there is not node voltage higher than voltage stabilization higher limit U _max, then return (4);

Situation 2, there is not node voltage lower than voltage stabilization lower limit U _minbut there are other node voltages higher than voltage stabilization higher limit U _max, then the voltage U reduction 1%U of direct current pressure side is determined in order _nif now there is node voltage lower than voltage stabilization lower limit U _min, then make enter (6); If now there is not node voltage lower than voltage stabilization lower limit U _min, then return (4);

Situation 3, neither there is node voltage higher than voltage stabilization higher limit U _max, there are not other node voltages lower than voltage stabilization lower limit U yet _min, calculate DC network loss now enter (6);

Above-mentioned DC network loss for line loss Δ P _ijwith converter loss Δ P _dctwo parts sum, if DC distribution netting twine road only exists resistance, then line loss computing formula is as follows:

${\mathrm{\ΔP}}_{ij}=I_b^2{R}_{ij}$

In formula, i, j are branch road two ends nodes numberings, I _bfor i node is to the branch current of j node, R _ijfor i node is to the branch resistance of j node.

The computing formula of converter loss is as follows:

${\mathrm{\ΔP}}_{dc}=P_{con}\left(i\right)+E=P_{loss}=K_1\·\left|I_{ac}\right|+K_2\·\left|I_{dc}\right|+(K_3+R_T)\·I_{ac}^2+K_4\·I_{dc}^2$

P in formula _coni () is converter on-state loss, E is converter switching loss, I _acfor converter ac-side current, I _dcfor Converter DC-side electric current, R _tfor connecting the all-in resistance of transformer and equivalent converter reactor, K _1-4be constant.

(6) make k increase by 1, if k≤n, then return step 3, if k>n, then enter (7);

(7) sorted by the n drawn a DC network loss value, performance number corresponding when adopting DC network loss minimum is as the performance number instruction determining direct current power end, and now corresponding voltage is as the voltage instruction value determining direct current pressure side.

In technique scheme, described is n section by determining direct current power end power divider, and its value can be: 2≤n≤1000.Wherein n can need value according to working control, and span is as follows: 2≤n≤1000.

The beneficial effects of the utility model are: native system works in for one end determines direct voltage mode, the other end works in the flexible direct current distribution system of two power ends determining direct current power mode, each node voltage and injecting power is obtained by the station Ore-controlling Role of load side detection and control terminal and converter, CPU is passed to by communication network, CPU sets up converter and DC line constraints accordingly, and it is minimum for target with whole distribution network system via net loss, calculate DC network optimal load flow, check the out-of-limit situation of node voltage of trying to achieve.If it is out-of-limit to there is node voltage, then carry out iteration adjustment until meet voltage stabilization condition according to the control method of central processing unit inside.Finally determine that DC distribution net is determined the voltage instruction value of direct current pressure side and determines the power command value of direct current power end, realize the control optimizing distribution power flow.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of the control system of optimization DC distribution net trend of the present utility model.

Fig. 2 is the algorithm flow chart of DC distribution net optimal power flow control system.

Embodiment

Below in conjunction with the drawings and specific embodiments, the utility model is further illustrated.

With reference to Fig. 1, the concrete performance of the utility model is as follows:

Fig. 1 illustrates the DC distribution net of a band two ends power supply, four DC loads, load side access current sensor and voltage sensor are in order to measure load side current value and magnitude of voltage to detection and control terminal, send central processing unit to via communication network, carry out issuing the converter of control command to corresponding end by communication network after computing draws result of calculation in central processing unit.First power distribution network network parameter and node injecting power information is read in.Assuming that each load power demand is followed successively by P _lD1, P _lD2, P _lD3, P _lD4, on bus, each branch resistance is followed successively by R ₁₂, R ₂₃, R ₃₄; VSC1, VSC2 are connected on node 1,4.Assuming that VSC1 determines direct current pressure side and voltage is U _vSC1, VSC2 is for determining direct current power end and power is P _vSC2, node serial number as shown in Figure 1.Determining direct current pressure side initial voltage value is rated voltage U _vSC1=U _n, determining direct current power end initial voltage value is wherein n (2≤n≤1000) is the interval sum determining the division of direct current power end rated power, for ease of illustrating, gets n=2 herein.Load flow calculation is carried out to power distribution network shown in Fig. 1, obtains each node voltage and be respectively U ₁, U ₂, U ₃, U ₄, U _vSC1and U _vSC2, each branch current is respectively I ₁₂, I ₂₃, I ₃₄, I _vSC1, I _vSC2.Check the out-of-limit situation of each node voltage:

Situation 1: suppose now node 2 voltage U ₂lower than minimum stable voltage U _min, then U is made _vSC1=U _n+ 1%U _nafter carry out Load flow calculation again, obtain one group of new node voltage after carry out the out-of-limit situation of inspection node voltage again.If still there is node voltage lower than minimum stable voltage U _minmake U further _vSC1=U _n+ 2%U _nafter again carry out Load flow calculation and obtain one group of new node voltage.Assuming that after amendment iteration m time, the new node voltage obtained all meet node voltage and stablize not out-of-limit condition, preserve now determine direct voltage terminal voltage suppose still there is node voltage lower than minimum stable voltage U in the node voltage obtained for the i-th-1 time in amendment iteration _min, but occurred that node voltage is higher than highest stabilizing voltage U in the node voltage that obtains for i-th time of amendment iteration _max, then this setting determine direct current power end performance number under cannot meet distribution network voltage stable condition, directly by the network loss Δ P in this set value of the power situation _loss=P _load=P _lD1+ P _lD2+ P _lD3+ P _lD4.

Situation 2: suppose now node 2 voltage U ₂higher than highest stabilizing voltage U _max, then U is made _vSC1=U _n-1%U _nafter carry out Load flow calculation again, obtain one group of new node voltage after carry out the out-of-limit situation of inspection node voltage again.If still there is node voltage higher than highest stabilizing voltage U _maxmake U further _vSC1=U _n-2%U _nafter again carry out Load flow calculation and obtain one group of new node voltage.Assuming that after amendment iteration m time, the new node voltage obtained all meet node voltage and stablize not out-of-limit condition, preserve now determine direct voltage terminal voltage suppose still there is node voltage higher than highest stabilizing voltage U in the node voltage obtained for the i-th-1 time in amendment iteration _max, but occurred that node voltage is lower than minimum stable voltage U in the node voltage that obtains for i-th time of amendment iteration _min, then this setting determine direct current power end performance number under cannot meet distribution network voltage stable condition, directly by the network loss Δ P in this set value of the power situation _loss=P _load=P _lD1+ P _lD2+ P _lD3+ P _lD4.

Situation 3: when each node voltage all meets voltage stabilization condition, DC network loss calculation is carried out to power distribution network.Via net loss is divided into two parts, wherein each branch current of obtaining according to last calculation of tidal current of line loss be R with each branch resistance in network parameter ₁₂, R ₂₃, R ₃₄line loss can be calculated the wherein converter side electric current I that obtains according to last calculation of tidal current of converter loss _vSC1, I _vSC2converter loss can be obtained added line loss can obtain and preserve and now correspondingly determine direct current power end set value of the power with determine direct voltage terminal voltage set point

Then reset that to determine direct voltage terminal voltage be U _vSC1=U _n, determining direct current power end power is repeat above-mentioned Load flow calculation, check that node voltage is stablized and via net loss calculates, obtain via net loss finally determining direct voltage terminal voltage is U _vSC1=U _n, determining direct current power end power is obtain via net loss

Further, to tried to achieve via net loss value sort, assuming that for the minimum value in three, then determine direct voltage terminal voltage value by its correspondence with determine direct current power end performance number vSC1 and VSC2 is issued to respectively as control command.

Although content of the present utility model has done detailed introduction by above preferred embodiment, will be appreciated that above-mentioned description should not be considered to restriction of the present utility model.After those skilled in the art have read foregoing, for multiple amendment of the present utility model and substitute will be all apparent.Therefore, protection range of the present utility model should be limited to the appended claims.

Claims (1)

1. optimize the control system of DC distribution net trend for one kind, it is characterized in that, comprise the communication network between the detection and control terminal of a CPU, some load sides and equivalent, two Converter Station Ore-controlling Role and all detection and control terminals, between CPU and each detection and control terminal and between CPU and two Converter Station Ore-controlling Role; Described detection and control terminal and load side one_to_one corresponding, for gathering the power of corresponding load side, in two described Converter Station Ore-controlling Role, one is constant DC voltage control current conversion station, and another is for determine direct current power current conversion station.