IEEE Power & Energy Magazine - March/April 2018 - 44

Based on the SGOS, a distributed backup control center
architecture has been established, which includes national,
regional, provincial, district, and county control centers.
equipment assets and ensured reliable power supply during
national grid major events and activities.

Assuring Controllability
of the Extra-Large Grid Operation
with the application of the sgos, multilevel collaborations
of systemwide agC and avC comprehensively enhanced the
controllability of large power grid operation. a remote control for 31,804 substations with more than 760,000 switches
and an automatic voltage control for 28,709 substations has
been realized in control centers at different levels in the
sgCC. This greatly reduces the workload of centralized
monitoring, improves the voltage control levels of the large
power grid, and effectively supports the integration of regulatory business requirements. agC with multilevel dispatching coordination has improved the stability of tie-line control
between the north China and Central China power grids.
Just like agC, the systemwide avC has been implemented
across control centers in China. Most of the generators have
closed-loop control by the avC system, which has become a
fundamental function for real-time control.

Enabling Collaborative Capability
Among Multilevel Control Centers
due to vertical interaction, all control centers at different levels
can use sgoss to execute real-time monitoring and control,
online dynamic security analysis, the day-ahead scheduling,
and security testing jointly. They use the same grid model,
real-time data, and basic operating mode. staff at the specialized
departments in the control centers at different levels calculate the
impact of different faults on the power grid, extract faults with
higher risk, and place them into a grid operational risk-sharing
pool. This strengthens the ex ante and ex post risk control for
the power grid and improves collaborative operations across
levels. a unified standard is built to help share dispatching
information vertically among control centers, which allows
for business interaction and process data exchange. The largescale, cross-regional power-flow data is shared among control
centers online. The generation scheduling and maintenance
plan in the control centers at different levels can be approved
systematically through the dispatching data network, which
improves the efficiency of coordinating dispatch.

Enhancing the Stability
of Very Large Power System Operation
The current power grid structure in China does not perform well enough to endure a serious fault, and problems in
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dynamic, transient, and thermal stability typically coexist.
The large-scale development of intermittent renewable energy
resources reduces power system stability performance. Traditional static security analysis based on a snapshot of power
flow cannot satisfy the requirement for analysis and decision
making for dynamic and uncertain power grid operation.
Monitoring power system variations, dynamic tracking, and
early-warning functions implemented in the sgos can analyze the stability performance of the power grid under cascading outages. it can issue a preventive control strategy for
dispatchers to cope with multiple contingencies and provide
the means to avoid power grid outages caused by multiple
equipment failures. Fault information is integrated and managed by an intelligence analysis and alarming (iaa) function.
based on the fault information collected, the iaa analyzes
the power grid fault causes and impacts and provides a report
on the system response. The iaa application sends a report
to all related control centers automatically.

Supporting the Optimal Allocation
of Power Resources in a Wider Scope
The sgos has established a coordinated control mechanism to promote the optimal allocation of power resources
in a wider scope. The hierarchical model predictive control
method in decision making is used for dispatching and control.
The decision making done in a shorter time period modifies
the results completed over a longer time period. Uncertainty
in both generation and load demand has been reduced and
absorbed by a layer-by-layer modification. Through vertical coordination among control centers, the full economy
and efficiency of dispatch scheduling has been achieved.
Through a closed-loop iteration between dispatch scheduling
and security checking, a coordination between economy and
security has also been realized.

Promoting the Effective Utilization
of Large-Scale Renewable Energy
based on the sgos, 26 provincial or higher-level control centers in China have established the dispatching function for
accommodating renewable energy covering over 1,300 wind
farms and more than 800 concentrated photovoltaic stations. Twenty provincial or higher-level control centers have
built a hydropower dispatching automation function covering
more than 600 hydropower stations. The application of the
sgos has promoted an effective accommodation of largescale renewable energy, resulting in a reduced percentage of
fossil energy production. as an example, the application of
march/april 2018

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2018