Solar aided coal-fired power generation system participating in primary frequency regulation and control method thereof

Patent metadata

Field	Value
Publication number	US-11236633-B2
Application number	US-201917279569-A
Country	US
Kind code	B2
Filing date	Jun 22, 2019
Priority date	Mar 13, 2019
Publication date	Feb 1, 2022
Grant date	Feb 1, 2022

Abstract

A solar aided coal-fired power generation system participating in primary frequency regulation and a control method thereof propose a system configuration with two regulation schemes by coupling medium-low-temperature solar collectors and a coal-fired generation unit. The two regulation schemes are a high-pressure feedwater bypass scheme and a low-pressure condensate bypass scheme. The present invention formulates a primary frequency regulation control logic, so as to efficiently and accurately participate in the primary frequency regulation, thereby keeping the power grid frequency rapidly stable. The present invention also formulates a working fluid outlet temperature control logic for the solar aided coal-fired thermal system, which adjusts a heat exchange working fluid flow of the solar collectors to ensure that the temperature in each section is stable during the primary frequency regulation. The present invention uses operation matching of the turbine system and the solar collectors to improve effectiveness of the primary frequency regulation.

First claim

What is claimed is:

1. A solar aided coal-fired power generation system participating in primary frequency regulation, comprising: a boiler ( 1 ), a steam turbine ( 2 ) connected to an outlet of the boiler ( 1 ), a high-pressure heater ( 3 ) connected to a high-pressure cylinder extraction port of the steam turbine ( 2 ), a deaerator ( 4 ) connected to a medium-pressure cylinder extraction port of the steam turbine ( 2 ), a low-pressure heater ( 5 ) connected to a low-pressure cylinder extraction port of the steam turbine ( 2 ), and a condenser ( 6 ) connected to a low-pressure cylinder exhaust port of the steam turbine ( 2 ); the solar aided coal-fired power generation system further comprises a high-pressure feedwater bypass regulation system and a low-pressure condensate bypass regulation system to enable two primary frequency regulation schemes consisting of a high-pressure feedwater bypass regulation scheme and a low-pressure condensate bypass regulation scheme:
1) in the scheme, feedwater at an outlet of the deaerator ( 4 ) is boosted by a feedwater pump ( 8 ) and divided into two paths, wherein one path passes through the high-pressure heater ( 3 ) and a feedwater valve ( 7 ) before entering the boiler ( 1 ), and the other path passes through a feedwater bypass valve ( 11 ) before entering a high-pressure bypass heat exchanger ( 12 ) to merge into the boiler ( 1 ); meanwhile, a heat exchange working fluid of the high-pressure bypass heat exchanger ( 12 ) is boosted by a high-pressure bypass pump ( 13 ) before entering a first solar collector ( 14 ) to absorb solar energy collected, and then enters the high-pressure bypass heat exchanger ( 12 ) to transfer heat to the feedwater; during the primary frequency regulation process, output power of the steam turbine ( 2 ) is rapidly changed by adjusting the feedwater bypass valve ( 11 ), thereby meeting requirements of the primary frequency regulation;
2) in the low-pressure condensate bypass regulation scheme, condensate at an outlet of the condenser ( 6 ) is boosted by a condensate pump ( 10 ) and divided into two paths, wherein one path passes through the low-pressure heater ( 5 ) and a deaerator inlet valve ( 9 ) before entering the deaerator ( 4 ), and the other path passes through a condensate bypass valve ( 15 ) before entering a low-pressure bypass heat exchanger ( 16 ) to merge into the deaerator ( 4 ); meanwhile, a heat exchange working fluid of the low-pressure bypass heat exchanger ( 16 ) is boosted by a low-pressure bypass pump ( 17 ) before entering a second solar collector ( 18 ) to absorb the solar energy collected, and then enters the low-pressure bypass heat exchanger ( 16 ) to transfer heat to the condensate; during the primary frequency regulation process, the output power of the steam turbine ( 2 ) is rapidly changed by adjusting the condensate bypass valve ( 15 ), thereby meeting requirements of the primary frequency regulation;
wherein a method for controlling the solar aided coal-fired power generation system participating in primary frequency regulation comprises formulating a primary frequency regulation control logic and a heater outlet temperature control logic according to operating characteristics of the solar aided coal-fired power generation system, which comprises specific steps of:
1) formulating the primary frequency regulation control logic:
according to an operating status of a power grid, obtaining a maximum frequency adjustment Δf max when the primary frequency regulation is needed, and then converting into a required maximum power adjustment ΔP max with a speed droop δ of a generation unit, which is:
Δ P max =f 1 (Δ f max )=Δ f max /δ

according to an actual operating status of the solar aided coal-fired power generation system, determining a maximum power adjustment ΔP LPH,max of the low-pressure condensate bypass regulation scheme, and comparing with the required maximum power adjustment ΔP max , wherein if ΔP max >ΔP LPH,max , the high-pressure feedwater bypass regulation scheme is selected for the primary frequency regulation; if ΔP max ≤ΔP LPH,max , the low-pressure condensate bypass regulation scheme is selected for the primary frequency regulation;
after determining a regulation scheme for the primary frequency regulation, obtaining a real-time frequency value f pv according to the operating state of the power grid, and comparing with a stable frequency value f sp required by the power grid, so as to calculate a frequency deviation Δf; setting parameters of the frequency deviation in a speed governor to obtain a power adjustment ΔP, wherein the parameters comprise a frequency modulation deadband and a speed droop:
Δ P=f 2 (Δ f )

superimposing an adjustment output Δμ, which is obtained by the power adjustment ΔP in a PID controller, on a control valve corresponding to the high-pressure feedwater bypass regulation scheme or the low-pressure condensate bypass regulation scheme, so as to generate a latest valve opening μ new :
μ new =μ old +Δμ

wherein μ old is an initial valve opening;
finally, applying an optimal scheme to the primary frequency regulation to form a closed-loop optimization control logic; and
2) formulating an outlet water temperature control logic for the high-pressure heater and the low-pressure heater:
for the primary frequency regulation with the high-pressure feedwater bypass regulation scheme, formulating the outlet water temperature control logic as:
first, using a temperature sensor to obtain a temperature T f,pv when the feedwater enters the boiler ( 1 ), and comparing the temperature T f,pv with a preset temperature T f,sp for the feedwater to enter the boiler ( 1 ), so as to obtain a temperature deviation ΔT 1 ; using the temperature sensor to obtain a temperature T s,pv when a working fluid of the first solar collector ( 14 ) enters the high-pressure bypass heat exchanger ( 12 ), and comparing the temperature T s,pv with a preset temperature T s,sp for the working fluid of the first solar collector ( 14 ) to enter the high-pressure bypass heat exchanger ( 12 ), so as to obtain a temperature deviation ΔT 2 ; accumulating the two temperature deviations to obtain a total temperature deviation ΔT h :
Δ T h =ΔT 1 +ΔT 2 ;

calculating the total temperature deviation ΔT h in the PID controller to obtain a direct control command Δ Ψh for the high-pressure bypass pump ( 13 ):
ΔΨ h =f (Δ T h );

meanwhile, due to long solar collector piping and large thermal inertia, processing a primary frequency regulation fast command with feedforward correction for temperature control of each section; and using a control command Δ μh for the feedwater bypass valve ( 11 ), which is obtained in the primary frequency regulation control logic of the high-pressure feedwater bypass regulation scheme, to generate a feedforward signal command Δ φh for the high-pressure bypass pump ( 13 ) through a function generator:
Δφ h =f (Δμ h )

finally, superimposing the direct control command Δ Ψh and the feedforward signal command Δ φh on the high-pressure bypass pump ( 13 ) to generate a latest speed command σ h,new thereof:
σ h,new =σ h,old −ΔΨ h −Δφ h

wherein: σ h,old is an initial speed of the high-pressure bypass pump ( 13 );
for the primary frequency regulation with the low-pressure condensate bypass regulation scheme, formulating the outlet water temperature control logic as: first, using the temperature sensor to obtain a temperature T c,pv when the condensate enters the deaerator ( 4 ), and comparing the temperature T c,pv with a preset temperature T c,sp for the condensate to enter the deaerator ( 4 ), so as to obtain a temperature deviation ΔT 3 ; using the temperature sensor to obtain a temperature T o,pv when a working fluid of the second solar collector ( 18 ) enters the low-pressure bypass heat exchanger ( 16 ), a

Assignees

• Univ Xi An Jiaotong

Inventors

• Yan Junjie
• Zhao Yongliang
• Liu Ming
• Chong Daotong

Classifications

• H02J2101/22

  Solar energy · CPC title

• F03G6/003 Primary

  having a Rankine cycle (F03G6/065 takes precedence) · CPC title

• F01K17/02

  for heating purposes, e.g. industrial, domestic (F01K17/06 takes precedence; domestic- or space-heating systems, e.g. central-heating systems, in general F24D1/00, F24D3/00, F24D9/00) · CPC title

• F01D15/10 Primary

  Adaptations for driving, or combinations with, electric generators · CPC title

• F28B9/08

  for collecting and removing condensate · CPC title