GB2608553A

GB2608553A - Power distribution method for power generator sets in DC grid

Info

Publication number: GB2608553A
Application number: GB2214622.9A
Authority: GB
Inventors: Yue Fan; Wu Yunxiang; Zhao Hongpin; Zhang Mingda; Liang Chaobo; Su Shijie; Chen Yun; Tang Wenxian
Original assignee: Wuxi Silent Electric System Ses Tech Co Ltd
Current assignee: Wuxi Silent Electric System Ses Tech Co Ltd
Priority date: 2020-03-18
Filing date: 2021-02-27
Publication date: 2023-01-04
Also published as: CN111404202A; CN111404202B; GB202214622D0; WO2021185057A1; GB2608553A8

Abstract

Disclosed is a power generator set in a DC grid power system, comprising at least two power supply mechanisms connected to a DC bus and a main control module. Each power supply mechanism comprises a power generator, which is sequentially connected to a circuit breaker, a rectifier power module, a fuse, and the DC bus. A current sensor is provided on the wire between the circuit breaker and the rectifier power module. A DC voltage sensor is provided on the wire between the rectifier power module and the fuse. The current sensor, the rectifier power module, and the DC voltage sensor are all electrically connected to an A/D sampling module. The A/D sampling module is electrically connected to a sub-controller. According to the power distribution method for power generator sets, in consideration of the impact of the change of a marine environment on the load power of a ship and the power consumed by the entire power system, the total load power of the system in an operating state can be obtained in real time, and by establishing a power distribution optimization model, the relationship between the proportion of the output power of diesel power generators and fuel consumption is accurately determined, thereby improving the accuracy of power distribution of power generator sets.

Description

POWER DISTRIBUTION METHOD FOR GENERATOR SETS IN DC

GRID

TECHNICAL FIELD

The present invention relates to a power distribution method for generator sets in a direct current (DC) grid.

BACKGROUND

For a waterborne vessel power station, in the case of not connecting to the large power grid, due to the small number of generator sets, the change of the load can easily change the power grid, and cause frequency fluctuation of the power grid, resulting in the uneven distribution of active loads of the generator sets. Even some generator sets are overloaded, and some generator sets operate as motors (operate at reverse power). The advantages and disadvantages of power distribution among generator sets of the waterborne vessel may have a direct impact on the stability and safety of power grid operation of the waterborne vessel. The relative capacity of a synchronous generator and the grid parallel with the synchronous generator has a great impact on the motor. Therefore, it is particularly important to discuss the power distribution and automatic adjustment of parallel synchronous generators in different scales of power grids.

It is found through retrieval of the existing literature that the Chinese Patent Application No. CN201710859634.6 discloses "a power distribution method for parallel operation of AC generator sets with an asymmetric structure". In the method, the power distribution controller identifies all AC generator sets as a host and a slave. A power distribution controller of the host controls thc host to operate at a rated frequency and a rated voltage, and a power distribution controller of the slave controls the slave to operate with an active power distribution adjustment target value and a reactive power distribution adjustment target value. However, the method is power distribution when the voltage difference of the generator set exceeds the set value, so that the output power of the generator set is balanced. In the method, the impact of the change of the driving environment of the waterborne vessel on the load power of the waterborne vessel and the power consumed by the entire power system are not considered. As a result, the PM S cannot accurately obtain the current total load power of the system, and thus cannot accurately distribute the power of the generator set. The journal "Application of Improved Droop Control in Parallel Operation of Waterborne Vessel Power Stations" in "Ship Engineering" (Issue 3, 2018) published by Wang Feihu and Gao Jian also provides a power distribution method. However, the power management system mentioned in the method cannot accurately determine the relationship between the proportion of the output power of diesel generators and fuel consumption, and cannot ensure that the generator set operates at the optimal economic time, resulting in energy waste.

SUMMARY

A solution to the technical problem in the present invention is to provide a power distribution method for generator sets in direct current (DC) grid, so as to reduce energy consumption.

In order to solve the above technical problem, the technical scheme adopted in the present invention is as follows. A generator set in a DC grid power system includes at least two generator-based power supply mechanisms connected to a DC bus and a main controller. Each of the generator-based power supply mechanisms includes a diesel generator, the diesel generator is sequentially connected to a circuit breaker, a rectifier power module, and a fuse through a power supply line, and the power supply line is finally connected to the DC bus. A current sensor is arranged on a wire between the circuit breaker and the rectifier power module, and a DC voltage sensor is arranged on a wire between the rectifier power module and the fuse. The current sensor, the rectifier power module, and the DC voltage sensor are all electrically connected to an AID sampling module, and the AO sampling module is electrically connected to a sub-controller. All sub-controllers are electrically connected to the main controller, and a power distribution method for generator sets in a DC grid includes the following steps: step a: setting parameters for each diesel generator and setting power parameters for each diesel generator set through the main controller, that is, respectively setting a lower limit PiT and an upper limit Pm of an optimal operating load power of an lth (1 = 1, 2, ..., N) diesel generator, and selecting a first diesel generator set as a default start item; step b: continuously detecting, by the main controller, a total power Pt of the DC grid power system, where when a load operates in the DC bus, the power generation system starts operating, and the first diesel generator set starts operating; calculating, by the sub-controller, a service power 1 of the first diesel generator set; and causing an alternating current (AC) generated by the first diesel generator set to pass through the rectifier power module, and setting rectifier parameters of the rectifier power module to keep a rectified voltage value within rimin _ VImax to ensure P" <P' <P1u -step c: calculating, by the main controller, a range of a total optimal operating load power of the diesel generator sets, where since only the first diesel generator set is in the operating state, a lower limit of the total optimal operating load power of the diesel generator sets is = r 11, and an upper limit of the total optimal operating load power of the diesel generator sets is ju h' * step d: successively determining, by the main controller, operating states of all of the diesel generator sets, where the sub-controller calculates a service power Pi of an id' diesel generator set if the in' diesel generator set is in an operating state; and causing the AC generated by the i diesel generator set to pass through the rectifier power module, and setting rectification parameters of the rectifier power module are set to keep the rectified V V P < P < P voltage value within llnin -rim to ensure 11 1; step e: calculating, by the main controller, the range of the total optimal operating load power of the diesel generator sets by using the following formula: the lower limit of the total optimal operating load power of the diesel generator sets P, being calculated by: it; and the upper limit of the total optimal operating load power of the diesel generator set being Pu = calculated by: * step 11 comparing, by the main controller, a total power P of the DC bus with the lower limit P and the upper limit P. of the total optimal operating load power of the diesel P < P < P. . . generator sets, where if E " , it indicates that a generating power of the each diesel generator is within the optimal operating load power range when a total generating power of the diesel generator sets reaches Pt and step (g) is performed, and if PI does not satisfy < Pt < , that is, when Pt Pu or Pt <Pi, step (h) is performed; step g: synchronously controlling, by the main controller, voltages of the diesel generators through the sub-controller according to a cross-coupling control strategy; step h: establishing an optimization model and solving an optimal operating sequence of the diesel generator sets, including: h-1: setting an existing operating generator sequence to W' OVAL-Wal-n -IV and a non-operating generator sequence to 2 124.1.,:4z,"''v:3.-x-ta& where Wi3 {123.,..*,,M; / = argmax-1 (P"" +P,(s')) h-2: calculating L 2 if i)t > , that is, finding a diesel generator from the non-operating diesel generators with a largest average optimal operating load power, then performing step h-3, and performing step h-4 if < 1; p (pr pi(Wi))± (pi,(S i) ± PS I t' h-3: calculating 2 2, where if P' < W WILtaa, S' (V, and L L +1, turning on the diesel generator with the largest average optimal operating load power found in step h-2, then performing step h-2, and performing step h-6 until P' >Pt; I = argmax -1) h-4: calculating ()L 2, that is, finding a diesel generator with a largest average optimal operating load power from the operating diesel generators: > P' -*3 p (W.) ± p(W i))_ p (\V) p(IV)) h-5: calculating te, 2' ' 2, where if I)" W W 5 U(Wa, and L t -1, turning on the diesel generator with the largest average optimal operating load power found in step h-4, then performing step h-4, and performing step h-6 until P"<PE; h-6: calculating 2 \ / 2 \ , where i = 1, 2, ..., N-L, that is, respectively calculating a difference between the average optimal operating load power of any diesel generator in the operating sequence and the average optimal operating load power a = 1 (,(si)±1,,(s,)) of any diesel generator in the non-operating sequence, where 2 and 0 _ 1 (p(W,) p(%)) -I") 2 " I * then calculating /,,/ = argmin (P(wL) + P(w))+ -P OL*riL where if I = 0, W=WU{S}, S=S \{s}, L=L-P1 if.1= 0, W=WAW4 S=SLAW11, L=L-1 if I, 0, W=WWWW3 S=SU{W,HS3 T=L the above process is the process of solving the optimal operating sequence of the diesel generators, that is, a maximum value Plum of PI and a minimum value Pumax of P. that P < Pt < Pu are found, so that the lower limit P P i and the upper limit satisfy i u of the total optimal operating load power of the diesel generator sets are closest to the total power t of the DC bus; if = 0, W=WU{S,}, S=S \{S L=L+1, which indicates that I = Pimax and Pi, = without turning off the diesel generator in the operating sequence; if j 0, W = W {WIk S=SU{V1}, L=L-I which indicates that PI=P'"IaN and PU PUMUX are satisfied after a diesel generator in an operating sequence is turned off without turning on the diesel generator in the non-operating sequence; and W=WU{S,}\{W,}, S=SUIVVHS,), L=L if J 0, which indicates that PI=Pmax and Pu=Pumn are satisfied after a diesel generator in the non-operating sequence is turned on and a diesel generator in the operating sequence is turned off; and h-7: upon completion of the above steps, that is, the process of optimizing and solving the optimal operating sequence of the diesel generator set is completed, periodically detecting, by the main controller, the total power Pi of the DC bus, if Pt changes, performing step 4, and if Pt does not change, ending the optimization, and maintaining the existing sequence of the diesel generator sets for operation.

As a preferred solution, step g includes the following: g-1: calculating, by the main controller, an average voltage r according to the current < < total power Pt of the DC grid system when, where < < PI is satisfied are satisfied after a diesel generator in a non-operating sequence is turned on when output voltages of all of the operating diesel generators are IP; g-2: sending, by the main controller, a voltage regulation command to each sub-controller after V' is calculated; g-3: controlling, by the sub-controller, the rectifier power module to adjust a rectified DC voltage value after receiving the voltage regulation command from the main controller; g-4: continuously feeding back, by an AD conversion module on each power generation circuit, the output voltage of the diesel generator to each sub-controller, and sending, by the sub-controller, the voltage data to the main controller through the bus; g-5: calculating, by the main controller, a difference between and each output voltage after obtaining the voltage data sent by the sub-controller on the power generation circuit, and sending a voltage compensation signal to the each sub-controller according to a voltage difference; g-6: controlling, by the sub-controller, the rectifier power module to adjust a rectified DC voltage value again after receiving the voltage compensation signal from the main controller; and g-7: cyclically performing the operations from step g-4.

As a preferred solution, in step b, the calculation method for calculating the service power P of the first diesel generator set by the sub-controller specifically includes: reading, by an AC current sensor, an AC /1 generated by the first diesel generator set, detecting, by the voltage sensor, a rectified DC voltage value, reading, by an A/D sampling module, data about /1 and rl, sending the data to the sub-controller, calculating, by the

V V

sub-controller, an AC voltage Acl according to /1 and 1 and then calculating, by the sub-controller, a service power 1 of the first diesel generator set by using the following P, = -shV,,,x I, x 0 formula, where 4) is a power factor.

As a preferred solution, in step c, the calculation method for calculating the service power Pi of the ith diesel generator set by the sub-controller specifically includes: reading, by an AC current sensor of a power generation circuit of the ith diesel generator set, an AC generated by the diesel generator set, detecting, by the voltage sensor, a rectified DC voltage Tr V value. , reading, by an AID sampling module, data about and, sending the data to the sub-controller, calculating, by the sub-controller, the AC voltage Ac' according to and 1 and then calculating, by the sub-controller, a service power ^ of the ith diesel P =1hTi ", x x 0 generator set by using the following formula ' , where 4) is a power factor.

As a preferred solution, step g-3 of controlling, by the sub-controller, the rectifier power module to adjust the rectified DC voltage value after receiving the voltage regulation command from the main controller specifically includes: sending, by the sub-controller, a control signal to the AID sampling module after receiving the voltage regulation command from the main controller, and sending, by the A/D sampling module, a PWM wave to the rectifier power module after receiving the signal, the PWM wave changing a duty cycle of an IGBT in the rectifier power module to adjust the rectified DC voltage value.

As a preferred solution, step g-6 of controlling, by the sub-controller, the rectifier power module to adjust the rectified DC voltage value again after receiving the voltage compensation signal from the main controller specifically includes: sending, by the sub-controller, a control signal to the Ai'D sampling module after receiving the voltage compensation signal from the main controller, and sending, by the A/D sampling module, a PWM wave to the rectifier power module after receiving the signal, the PWM wave changing a duty cycle of an IGBT in the rectifier power module to adjust the rectified DC voltage value.

The beneficial effects of the present invention arc as follows. According to the power distribution method for diesel generator sets, the impact of changes in the marine environment on the load power of the waterborne vessel and the power consumed by the entire power system arc considered, the total load power under the operating state of the system can be accurately obtained in real time, and the relationship between the output power ratio of diesel generators and fuel consumption can be accurately determined by establishing a power distribution optimization model. In this way, the power allocation accuracy of a generator set is improved, and it is ensured that the generator set is running in a most fuel-efficient state, thereby improving the energy efficiency and reducing energy waste and pollution.

Different from the disadvantage that only two diesel generators can be controlled through traditional cross-coupling control, according to the control method adopted in the method, a plurality of diesel generators can be controlled simultaneously. The sub-controller of each diesel generator set continuously interacts with the main controller, and the status of each diesel generator is compared with the target value to implement separate compensation for each diesel generator. In this way, the voltage value of each diesel generator set can be effectively and quickly adjusted to the target state when the total system power changes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a circuit structure of a power generation system.

FIG. 2 is a schematic diagram of a power distribution process for a waterborne vessel.

In the figures: 1-Sub-controller, 2-Diesel generator, 3-Circuit breaker, 4-Current sensor, 5-Rectifier power module, 6-Fuse, 7-DC voltage sensor, 8-AID sampling module, 9-DC bus, 10-Main controller.

DETAILED DESCRIPTION

Specific implementations of the present invention are described in detail below with reference to the accompanying drawings.

As shown in FIG. 1 and FIG. 2, a generator set in a direct current (DC) grid power system includes N generator-based power supply mechanisms connected to a DC bus 9 and a main controller 10. Each of the generator-based power supply mechanisms includes a diesel generator 2, the diesel generator 2 is sequentially connected to a circuit breaker 3, a rectifier power module 5, and a fuse 6 through a power supply line, and the power supply line is finally connected to the DC bus 9. A current sensor 4 is arranged on a wire between the circuit breaker 3 and the rectifier power module 5, and a DC voltage sensor 7 is arranged on a wire between the rectifier power module 5 and the fusc 6. The current sensor 4, the rectifier power module 5, and the DC voltage sensor 7 are all electrically connected to an MD sampling module 8, and the A/D sampling module 8 is electrically connected to a sub-controller I. All sub-controllers I are electrically connected to the main controller 10, and a power distribution method for generator sets in a DC grid includes the following steps: (a): setting parameters for each diesel generator and setting power parameters for each diesel generator set through the main controller 10, that is, respectively setting a lower limit il and an upper limit P" of an optimal operating load power of an ith (1 = 1, 2, ..., N) diesel generator, and selecting a first diesel generator set as a default start item; (b) continuously detecting, by the main controller 10, a total pow er of the power system in the DC grid 9, where when the load operates in the DC bus 9, the power generation system starts operating, and the first diesel generator set starts operating; reading, by the current sensor 4, an AC 11 generated by the first diesel generator set, detecting, by the voltage sensor 7, a rectified DC voltage value 171, reading, by an AD sampling module 8, data about /I and H, sending the data to a sub-controller 1 through a bus, calculating, by the sub-controller 1, an AC voltage VAC' according to 11 and 1, and then calculating, by the sub-controller 1, a service power PI of the first diesel generator set by using the following formula: =1iV1xJ1xØ causing the generated AC to pass through the rectifier power module 5, and setting rectification parameters of the rectifier power module 5 to keep the rectified voltage value 050V within Vinun -PrImax to ensure PIr < <hi, where in this embodiment, and V, =1 1 0 0 V (c) calculating, by the main controller 10, a range of a total optimal operating load power of the diesel generator sets, where since only the first diesel generator set is in the operating state, a lower limit of the total optimal operating load power of the diesel generator sets is P= I PlI, and an upper limit of the total optimal operating load power of the diesel generator = p sets is 11 hi * (d) successively determining, by the main controller, operating states of all of the diesel generator sets, if an ith diesel generator set is in an operating state, reading, by the AC current sensor 4 of a generator circuit, an AC generated by the diesel generator set, detecting, by the voltage sensor 7, a rectified DC voltage value, reading, by an AD sampling module 8, data about and Vsending the data to the sub-controller 1, calculating, by the

V

sub-controller 1, the AC voltage:cc' according to 11 and [I and then calculating, by the sub-controller 1, a service power Pi of the it" diesel generator set by using the following formula: P, =1,5VA, x x 0 causing the generated AC to pass through the rectifier power module 5, and setting rectification parameters of the rectifier power module 5 to keep the rectified voltage value V V P < P < P within mini - x to ensure 1./ 1 1** * (e) calculating, by the main controller 10, the range of the total optimal operating load power of the diesel generator sets by using the following formula: the lower limit of the total optimal operating load power of the diesel generator sets being calculated by: = EP, 1=, the upper limit of the total optimal operating load power of the diesel generator sets being calculated by: = (1) comparing, by the main controller 10, a total power P1 of the DC bus 9 with the lower limit PI and the upper limit u of the total optimal operating load power of the diesel generator sets, where if P' < , it indicates that a generating power of the each diesel generator is within the optimal operating load power range when a total generating power of the diesel generator sets reaches and step (g) of synchronously controlling the voltages of the diesel generators according to the cross-coupling control strategy is performed, and if PI does not satisfy P-1 <P < , that is, when PI Pu or P < , step (h) of establishing the optimization model and solving the optimal operating sequence of the diesel generator sets is performed; (g) synchronously controlling the voltages of the diesel generators according to the cross-coupling control strategy, including

-

(g.1): calculating, by the main controller 10, an average voltage according to the current total power Pt of the DC grid system when P < < P, where V' satisfies: P <Pt < Pu when output voltages of all of the operating diesel generators are all II"; (g.2) sending, by the main controller 10, a voltage regulation command to each sub-controller 1 after r is calculated; (g.3) sending, by the sub-controller 1, a control signal to the A/D sampling module 8 after receiving the voltage regulation command from the main controller 10, and sending, by the AID sampling module 8, a PWM wave to the rectifier power module 5 after receiving the signal, the PWM wave changing a duty cycle of an IGBT in the rectifier power module to adjust the rectified DC voltage value;

U

(g.4) continuously feeding back, by an A/D conversion module 8 on each power generation circuit, the output voltage of the diesel generator to the each sub-controller 1, and sending, by the sub-controller 1, the voltage data to the main controller 10 through the bus; (g.5) calculating, by the main controller 10, a difference between and each output voltage after obtaining the voltage data sent by the sub-controller 1 on the power generation circuit, and sending, by the main controller 10, a voltage compensation signal to the each sub-controller 1 according to a voltage difference; (g.6) sending, by the sub-controller 1, a control signal to the AID sampling module 8 after receiving the voltage compensation signal from the main controller 10, and sending, by the AID sampling module 8, a PWM wave to the rectifier power module 5 after receiving the signal, the PWM wave changing a duty cycle of an IGBT in the rectifier power module to adjust the rectified DC voltage value; (g.7) cyclically performing the operations from step (g.4); (h) establishing the optimization model and solving the optimal operating sequence of the diesel generator sets, including: 11-1: setting an existing operating generator sequence to W' flt /AV and a non-operating generator sequence to 2 -[IPIP'Sz-,-1J., where J = a rg max -1 (Pu(sI) + )) h-2: calculating IN-L 2 if PI > Pu, that is, finding a diesel generator from the non-operating diesel generators with a largest average optimal operating load power, then performing step (h.3), and performing step (h.4) if P (T),(wi) pi(w i))+1 ()CS,) (Si)) iH 2 I 2 " Lk), °[= S and and L L + 1, turning on the diesel generator with the largest average optimal operating load power found in step h-2, then performing step h-2, and performing step h-6 until >1), ; = argmax-1 (Ptfwi + Pt(w. )) h-4: calculating 01 jiL 2, that is, finding a diesel generator with a largest average optimal operating load power from the operating diesel generators; h-3: calculating where if -V < h-5: calculating Pr' = P1(w1) where if P" > 2 -1(13,w1) Pi(w I)) LLCM), d - turning on the diesel generator with the largest average optimal operating load power found in step h-4, then performing step h-4, and performing step h-6 until p" < t * h-6: calculating (pu(s)) 1 0,,,,a( ) pi) 2 / 2, where i = 1,2, ..., N-L, that is, respectively calculating a difference between the average optimal operating load power of any diesel generator in the operating sequence and the average optimal operating load power 00 _ I fr(s,) of any diesel generator in the non-operating sequence, where 2 and = __1 (i3,0 2 then calculating I,J= argmin ( 0<i<T,0<j*V-I L p(mi) td 2 u where if I = 0, W=WU{S.,}, S=S\{S}, L=L+1 if J = 0, w = w s=sUlw, L=L-1 if I, J 0, w = w u {S,}\ kJ-S. = S {W, }\S, L=L the above process is the process of solving the optimal operating sequence of the diesel generators, that is, a maximum value finsx of I and a minimum value Pusin r Pu that satisfy P' < P < Pu are found, so that the lower limit Pr and the upper limit Pi of the total optimal operating load power of the diesel generator sets are closest to the total power PI of the DC bus 9; if = 0, W = WU {S J, S = S \ {S,}, L=L+1, which indicates that P = Pthin and Punax are satisfied after a di ii = esel generator in a non-operating sequence is turned on without turning off the diesel generator in the operating sequence; if J = 0, W = W {WI}"C = S U {WI k L=L-1, which indicates that PI = are satisfied after a diesel generator in an operating sequence is turned off without turning on the diesel generator in the non-operating sequence; and Plmax and W=WU{S,}\{W,1"5. =SUIW,HS,}, /.=/, if I, J # 0, , which indicates that = 11= Pim"' and Pit Pumin are satisfied after a diesel generator in the non-operating sequence is turned on and a diesel generator in the operating sequence is turned off; and h-7: upon completion of the above steps, that is, the process of solving the optimal operating sequence of the diesel generator sets is completed, periodically detecting, by the main controller 10, the total power Pt of the DC bus 9, if Pt changes, performing step (d) and if Pr does not change, ending the optimization, and maintaining the existing sequence of the diesel generator sets for operation.

The above embodiments only exemplarily describe the principles and effects of the present invention, and some applied embodiments arc not intended to limit the present invention. It should be noted that a person of ordinary skill in the art may further make several modifications and improvements without departing from the inventive concept of the present invention, which all fall within the protection scope of the present invention.

Claims

CLAIMSWhat is claimed is: 1.A generator set in a direct current (DC) grid power system, comprising at least two generator-based power supply mechanisms connected to a DC bus and a main controller, wherein each of the generator-based power supply mechanisms comprises a diesel generator, the diesel generator is sequentially connected to a circuit breaker, a rectifier power module, and a fuse through a power supply line, and the power supply line is finally connected to the DC bus; a current sensor is arranged on a wire between the circuit breaker and the rectifier power module, a DC voltage sensor is arranged on a wire between the rectifier power module and the fuse, the current sensor, the rectifier power module, and the DC voltage sensor are all electrically connected to an A/D sampling module, and the AD sampling module is electrically connected to a sub-controller; all sub-controllers are electrically connected to the main controller, and a power distribution method for generator sets in a DC grid comprises the following steps: step a: setting parameters for each diesel generator and setting power parameters for each diesel generator set through the main controller, that is, respectively setting a lower limit ii and an upper limit i" of an optimal operating load power of an (i = 1, 2, ..., N) diesel generator, and selecting a first diesel generator set as a default start item; step b: continuously detecting, by the main controller, a total power P, of the DC grid power system, wherein when a load operates in the DC bus, the power generation system starts operating, and the first diesel generator set starts operating; calculating, by the sub-controller, a service power PI of the first diesel generator set; and causing an alternating current (AC) generated by the first diesel generator set to pass through the rectifier power module, and setting rectifier parameters of the rectifier power module to keep a rectified voltage value within rimm lima', to ensure PH < < step c: calculating, by the main controller, a range of a total optimal operating load power of the diesel generator sets, wherein since only the first diesel generator set is in the operating state, a lower limit of the total optimal operating load power of the diesel generator sets is PT = PIT and an upper limit of the total optimal operating load power of the diesel P = P generator sets is " ' step d: successively determining, by the main controller, operating states of all of the diesel generator sets, wherein the sub-controller calculates a service power Pi of an ith diesel generator set if the ith diesel generator set is in an operating state; and causing the AC generated by the ith diesel generator set to pass through the recti ner power module, and setting rectification parameters of the rectifier power module are set to keep the rectified voltage value within IT V to ensure <T < itnin -Imax step e: calculating, by the main controller, the range of the total optimal operating load power of the diesel generator sets by using the following formula: the lower limit of the total optimal operating load power of the diesel generator sets Pj =EP] being calculated by: i=1; and the upper limit of the total optimal operating load power of the diesel generator set being calculated by: step f: comparing, by the main controller, a total power Pt of the DC bus with the lower limit P1 and the upper limit Pa of the total optimal operating load power of thePPdiesel generator sets, wherein if PI < < , it indicates that a generating power of the each diesel generator is within the optimal operating load power range when a total generating power of the diesel generator sets reaches t, and step (g) is performed, and if Pt does notPP PPsatisfy P' < < , that is, when > or Pi < Pl, step (h) is performed; step g: synchronously controlling, by the main controller, voltages of the diesel generators through the sub-controller according to a cross-coupling control strategy; step h: establishing an optimization model and solving an optimal operating sequence of the diesel generator sets, comprising: h-l: setting an existing operating generator sequence to I'S =' and a non-operating generator sequence to SK-z,l, wherein = argmax (p:S pi(S i))P Ph-2: calculating L 2 > if I, that is, finding a diesel generator from the non-operating diesel generators with a largest average optimal operating load power, then performing step h-3, and performing step h-4 if Pt <P; W S = EN); h-3: calculating pr V _(!),(v, i) ))± 1(1)(6 + pi(SJ)) , wherein if Pt < 1.47 -'5" IU(Sa:811/4 Oa, and)1;* +1, turning on the diesel generator with the largest average optimal operating load power found in step h-2, then performing step h-2, and performing step h-6 until P' >Pt; I = argmax ().L 2 (I)"(wi)) h-4: calculating, that is, finding a diesel generator with a largest average optimal operating load power from the operating diesel generators: pff = 2 2 (1),(Wi) pi(W,))_ (7),03/4)I Ih-5: calculating, wherein if Pif > 3 5 5 U Ut a, and t L -1, turning on the diesel generator with the largest average optimal operating load power found in step h-4, then performing step h-4, and performing step h-6 until P" < t h-6: calculating Qi = 1 bAsi)± pibi))_ 1, wherein i = 1, 2, ..., N-L, that is, 2 ' 2 respectively calculating a difference between the average optimal operating load power of any diesel generator in the operating sequence and the average optimal operating load power 0 _ I fri(s,) "(s)) of any diesel generator in the non-operating sequence, wherein 2 and (910= __1 (pie?, 2 then calculating /,./ = argmin +Th 1 (r,(wi)±pi()) 2 0 --L -wherein if I = 0, W =WLAS3 S =S \ISA, P=L+1 if J= 0, W =W S=SU{Wi}. L=L-1 if I, J 0, W =W JCS JAW S SUfWAS A, L=L the above process is the process of solving the optimal operating sequence of the diesel generators, that is, a maximum value 'max of I and a minimum value P"m"x of that satisfy PT < Pt < Pu are found, so that the lower limit Pi and the upper limit of the totalPoptimal operating load power of the diesel generator sets are closest to the total power ' of the DC bus; if I = 0, W = {S,} S = \ {S,}, L= L +1 P P which indicates that I = 'max and PP. = "ax are satisfied after a diesel generator in a non-operating sequence is turned on without turning off the diesel generator in the operating sequence; if J = 0, W=W\{WT}, S=SU{W4 L=L-1 which indicates that PI= PImax and P11 = Pumax are satisfied after a diesel generator in an operating sequence is turned off without turning on the diesel generator in the non-operating sequence; and f.1 0, W = W {S, \ NO, S = S {WI} \ {Si}' hich indicates that PI = Plmax i and P"=Pumax are satisfied after a diesel generator in the non-operating sequence is turned on and a diesel generator in the operating sequence is turned off; and h-7: upon completion of the above steps, that is, the process of optimizing and solving the optimal operating sequence of the diesel generator set is completed, periodically detecting, by the main controller, the total power Pt of the DC bus, if Pt changes, performing step 4, and if PI does not change, ending the optimization, and maintaining the existing sequence of the diesel generator sets for operation.
2. The power distribution method for generator sets in a DC grid according to claim 1, wherein step g comprises: g-1: calculating, by the main controller, an average voltage according to the current total power Pt of the DC grid system when P' < Pt < Pu, wherein P' < < Pu is satisfied when output voltages of all of the operating diesel generators are r; g-2: sending, by the main controller, a voltage regulation command to each sub-controller after r is calculated; g-3: controlling, by the sub-controller, the rectifier power module to adjust a rectified DC voltage value after receiving the voltage regulation command from the main controller; g-4: continuously feeding back, by an AID conversion module on each power generation circuit, the output voltage of the diesel generator to each sub-controller, and sending, by the sub-controller, the voltage data to the main controller through the bus; g-5: calculating, by the main controller, a difference between v and each output voltage after obtaining the voltage data sent by the sub-controller on the power generation circuit, and sending a voltage compensation signal to the each sub-controller according to a voltage difference; g-6: controlling, by the sub-controller, the rectifier power module to adjust a rectified DC voltage value again after receiving the voltage compensation signal from the main controller; and g-7: cyclically performing thc operations from step g-4; 3. The power distribution method for generator sets in a DC grid according to claim 2, wherein in step b, the calculation method for calculating the service power PI of the first diesel generator set by the sub-controller specifically comprises: reading, by an AC current sensor, an AC /I generated by the first diesel generator set, detecting, by the voltage sensor, a rectified DC voltage value H, reading, by an AID sampling module, data about I-I and r1, sending the data to the sub-controller, calculating, by the sub-controller, an AC voltage VAC I
ITaccording to /1 and 1, and then calculating, by the sub-controller, a service power 1 of the first diesel generator set by using the following formula 1 ACI x /1 x 0, 'herein (I) is a power factor.
4. The power distribution method for generator sets in a DC grid according to claim 2, wherein in step c, the calculation method for calculating the service power P1 of the ith diesel generator set by the sub-controller specifically comprises: reading, by an AC current sensor of a power generation circuit of the ith diesel generator set, an AC /1 generated by the diesel generator set, detecting, by the voltage sensor, a rectified DC voltage value ri reading, by an A/D sampling module, data about and r/i, sending the data to the sub-controller,V Vcalculating, by the sub-controller, the AC voltage AC according to TI and I, and then calculating, by the sub-controller, a service power Pi of the ith diesel generator set by using /3, =IRV x x 0 the following formula.4C71, wherein 4, is a power factor.
5. The power distribution method for generator sets in a DC grid according to claim 3 or 4, wherein step g-3 of controlling, by the sub-controller, the rectifier power module to adjust g the rectified DC voltage value after receiving the voltage regulation command from the main controller specifically comprises: sending, by the sub-controller, a control signal to the AID sampling module after receiving the voltage regulation command from the main controller, and sending, by the A/D sampling module, a PWM wave to the rectifier power module after receiving the signal, the PWM wave changing a duty cycle of an IGBT in the rectifier power module to adjust the rectified DC voltage value.
6. The power distribution method for generator sets in a DC grid according to claim 3 or 4, wherein step g-6 of controlling, by the sub-controller, the rectifier power module to adjust the rectified DC voltage value again after receiving the voltage compensation signal from the main controller specifically comprises: sending, by the sub-controller, a control signal to the A/D sampling module after receiving the voltage compensation signal from the main controller, and sending, by the A/D sampling module, a PWM wave to the rectifier power module after receiving the signal, the PWM wave changing a duty cycle of an IGBT in the rectifier power module to adjust the rectified DC voltage value.